GDAL bounding box differences in NAD27 - diff in tif?

wget http://estuarinebathymetry.noaa.gov/P090/P090_B90.zip
unzip P090_B90.zip

# /usr/bin is gdal 1.6.3 from ubuntu 10.04
# no path is gdal 1.9.0
/usr/bin/gdal_translate -of GTiff P090_37122DSQ_BIG.{dem,tif}

gdalinfo P090_37122DSQ_BIG.dem > P090_37122DSQ_BIG.dem.info.1.9.0
/usr/bin/gdalinfo P090_37122DSQ_BIG.dem > P090_37122DSQ_BIG.dem.info.1.6.3

grep "Upper Left" P090_37122DSQ_BIG.dem.info.1.{6.3,9.0}
P090_37122DSQ_BIG.dem.info.1.6.3:Upper Left  (-122.5479167,  38.1937500)
P090_37122DSQ_BIG.dem.info.1.9.0:Upper Left  (-122.5479167,  38.1937500) (122d32'52.50"W, 38d11'37.50"N)

/usr/bin/gdal_translate -of GTiff P090_37122DSQ_BIG.{dem,tif}

gdalinfo P090_37122DSQ_BIG.tif > P090_37122DSQ_BIG.tif.info.1.9.0
/usr/bin/gdalinfo P090_37122DSQ_BIG.tif > P090_37122DSQ_BIG.tif.info.1.6.3

grep "Upper Left" P090_37122DSQ_BIG.tif.info.1.{6.3,9.0}
P090_37122DSQ_BIG.tif.info.1.6.3:Upper Left  (-122.5479167,  38.1937500) P090_37122DSQ_BIG.tif.info.1.9.0:Upper Left  (-122.5483333,  38.1941667) (122d32'54.00"W, 38d11'39.00"N)

gdalinfo P090_37122DSQ_BIG.dem
Driver: USGSDEM/USGS Optional ASCII DEM (and CDED)
Files: P090_37122DSQ_BIG.dem
Size is 678, 897
Coordinate System is:
GEOGCS["NAD27",
    DATUM["North_American_Datum_1927",
        SPHEROID["Clarke 1866",6378206.4,294.978698213898,
            AUTHORITY["EPSG","7008"]],
        AUTHORITY["EPSG","6267"]],
    PRIMEM["Greenwich",0,
        AUTHORITY["EPSG","8901"]],
    UNIT["degree",0.0174532925199433,
        AUTHORITY["EPSG","9108"]],
    AUTHORITY["EPSG","4267"]]
Origin = (-122.547916666666666,38.193750000000001)
Pixel Size = (0.000833333333333,-0.000833333333333)
Metadata:
  AREA_OR_POINT=Point
Corner Coordinates:
Upper Left  (-122.5479167,  38.1937500) (122d32'52.50"W, 38d11'37.50"N)
Lower Left  (-122.5479167,  37.4462500) (122d32'52.50"W, 37d26'46.50"N)
Upper Right (-121.9829167,  38.1937500) (121d58'58.50"W, 38d11'37.50"N)
Lower Right (-121.9829167,  37.4462500) (121d58'58.50"W, 37d26'46.50"N)
Center      (-122.2654167,  37.8200000) (122d15'55.50"W, 37d49'12.00"N)
Band 1 Block=678x897 Type=Float32, ColorInterp=Undefined
  NoData Value=-32767
  Unit Type: m


gdalinfo P090_37122DSQ_BIG.tif
Driver: GTiff/GeoTIFF
Files: P090_37122DSQ_BIG.tif
Size is 678, 897
Coordinate System is:
GEOGCS["NAD27",
    DATUM["North_American_Datum_1927",
        SPHEROID["Clarke 1866",6378206.4,294.9786982139006,
            AUTHORITY["EPSG","7008"]],
        AUTHORITY["EPSG","6267"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4267"]]
Origin = (-122.548333333333332,38.194166666666668)
Pixel Size = (0.000833333333333,-0.000833333333333)
Metadata:
  AREA_OR_POINT=Point
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (-122.5483333,  38.1941667) (122d32'54.00"W, 38d11'39.00"N)
Lower Left  (-122.5483333,  37.4466667) (122d32'54.00"W, 37d26'48.00"N)
Upper Right (-121.9833333,  38.1941667) (121d59' 0.00"W, 38d11'39.00"N)
Lower Right (-121.9833333,  37.4466667) (121d59' 0.00"W, 37d26'48.00"N)
Center      (-122.2658333,  37.8204167) (122d15'57.00"W, 37d49'13.50"N)
Band 1 Block=678x3 Type=Float32, ColorInterp=Gray
  NoData Value=-32767

diff -r P090_37122DSQ_BIG.{dem,tif}.info.1.6.3
1,2c1,2
< Driver: USGSDEM/USGS Optional ASCII DEM (and CDED)
< Files: P090_37122DSQ_BIG.dem
---
> Driver: GTiff/GeoTIFF
> Files: P090_37122DSQ_BIG.tif
7c7
<         SPHEROID["Clarke 1866",6378206.4,294.978698213898,
---
>         SPHEROID["Clarke 1866",6378206.4,294.9786982139006,
9d8
<         TOWGS84[-3,142,183,0,0,0,0],
11,14c10,11
<     PRIMEM["Greenwich",0,
<         AUTHORITY["EPSG","8901"]],
<     UNIT["degree",0.0174532925199433,
<         AUTHORITY["EPSG","9108"]],
---
>     PRIMEM["Greenwich",0],
>     UNIT["degree",0.0174532925199433],
19a17,18
> Image Structure Metadata:
>   INTERLEAVE=BAND
26c25
< Band 1 Block=678x897 Type=Float32, ColorInterp=Undefined
---
> Band 1 Block=678x3 Type=Float32, ColorInterp=Gray
28d26
<   Unit Type: m


diff -r P090_37122DSQ_BIG.{dem,tif}.info.1.9.0
1,2c1,2
< Driver: USGSDEM/USGS Optional ASCII DEM (and CDED)
< Files: P090_37122DSQ_BIG.dem
---
> Driver: GTiff/GeoTIFF
> Files: P090_37122DSQ_BIG.tif
7c7
<         SPHEROID["Clarke 1866",6378206.4,294.978698213898,
---
>         SPHEROID["Clarke 1866",6378206.4,294.9786982139006,
10,13c10,11
<     PRIMEM["Greenwich",0,
<         AUTHORITY["EPSG","8901"]],
<     UNIT["degree",0.0174532925199433,
<         AUTHORITY["EPSG","9108"]],
---
>     PRIMEM["Greenwich",0],
>     UNIT["degree",0.0174532925199433],
15c13
< Origin = (-122.547916666666666,38.193750000000001)
---
> Origin = (-122.548333333333332,38.194166666666668)
18a17,18
> Image Structure Metadata:
>   INTERLEAVE=BAND
20,25c20,25
< Upper Left  (-122.5479167,  38.1937500) (122d32'52.50"W, 38d11'37.50"N)
< Lower Left  (-122.5479167,  37.4462500) (122d32'52.50"W, 37d26'46.50"N)
< Upper Right (-121.9829167,  38.1937500) (121d58'58.50"W, 38d11'37.50"N)
< Lower Right (-121.9829167,  37.4462500) (121d58'58.50"W, 37d26'46.50"N)
< Center      (-122.2654167,  37.8200000) (122d15'55.50"W, 37d49'12.00"N)
< Band 1 Block=678x897 Type=Float32, ColorInterp=Undefined
---
> Upper Left  (-122.5483333,  38.1941667) (122d32'54.00"W, 38d11'39.00"N)
> Lower Left  (-122.5483333,  37.4466667) (122d32'54.00"W, 37d26'48.00"N)
> Upper Right (-121.9833333,  38.1941667) (121d59' 0.00"W, 38d11'39.00"N)
> Lower Right (-121.9833333,  37.4466667) (121d59' 0.00"W, 37d26'48.00"N)
> Center      (-122.2658333,  37.8204167) (122d15'57.00"W, 37d49'13.50"N)
> Band 1 Block=678x3 Type=Float32, ColorInterp=Gray
27d26
<   Unit Type: m