I've actually never burned my fingers while doing that with a glass or ceramic V60. They probably do get hotter, but to me the main reasons for not using plastic is that unless you've used the dripper a lot already, plastics will vent that "plastic smell" which I believe to be VOCs, but I could be wrong. This effect is further exaggerated when the plastic is heated, which causes a sort of off-odor and off-taste to your coffee. But then again, I believe in pre-rinsing paper filters too, so if you don't usually pre-rinse your paper filters then maybe you won't notice this. I could be just extremely particular, or its a psychological thing.