Replying to this tweet: https://twitter.com/arubaarubandale/status/917843796100075521

So you saw from that first example with MegaZard Y and Venusaur that Venusaur didn't get its Chlorophyll Speed boost, right? The following 3 examples (Mega Evolving Kang, switching in Rain for Kingdra, and the Mega Evolution with TTar) are just there to show that partners never benefit from this Speed change, only the Megas themselves.