This yeast temperature thing is pretty wide spread...
Dr Cone, the bloke from Danstar Yeast, is on record as saying most yeast strain optimum rehydration temperature is closer to 40C. You can Google that easily enough.
Course one might choose not to believe the lead scientist of a yeast lab with a phd in microbiology... but I can tell you, I rehydrated S-04 at 40C and got a very thin layer of dead cells (high viability), thing went off like a rocket in the fermenter.
You are in zero danger of killing yeast with these temperatures. The thing that kills yeast is pitching it directly onto wort. Not all of it, but a lot of it. Fortunately they put a lot of cells in those dried packets...
I deliberately pitch into wort a bit warmer than then desired fermentation temp - purely because it'll get going faster, which is safer obviously. 99% of the fermentation will occur at the desired temperature so any funny flavours should not, by my inexpert reckoning, be much of a problem.