That is why beer bottles are shaped the way they are. The change from the wide bottom to the narrow neck is designed to allow you to slowly decant the beer(pour the beer off while leaving the yeast in the bottom).
If I rehydrate my yeast at 100F (I assume this is optimum temperature for yeast growth). Why should I not pitch it at close to the same temperature (accounting for cooling and such)? 60-75F seems low.