tbh most of it is very accurate. Maybe with exception of I rhythms but they're not used that often anyways. In the 2021 standard, all chX or CXi have 36s-based total length. In the past we have ch7/8/9, but now they are C7u/C8u/C9u, and writing them as ch7/8/9 is considered very bad and naughty. Same to C7i (now ch4-N) and C8i (now C6i-N).

For Ix, they don't require exactly two decel waves. The exact definition is: "daytime rhythms that 1. use two ice cards 2. do not use 36s-based total length 3. entail cob reuse". Really simple example is I4i: I-PPdd | I-PPdd (15.5, 15.5) (https://www.youtube.com/watch?v=Mrsry1uDfYY), which requires 10 cob (although it only has 8 written P). It's clearer if you expand it a bit: I-PPdd (15.5s *3), where you can see you hv a 45s total length and 12 written P, which makes sense to be played by 10 cob.