As long as I've been using that thing I never gave it much thought  ,

but I guess the plastic right at the blade reaches it's glass transition temperature  , assisting in that displacement of material .

The heat can't dissipate fast enough with deeper cuts  so you get significant material melting .

I know when I'm plowing thru , roughing parts out  ,when I pull the blade away I'll get that fresh out of the oven pizza cheese string .

the heat is definitely there