Again with the premature assumptions. I am a proffesional logger of 10+ years myself.
I'm telling the OP that he (or the home owner) that he may wish to attept to wedge that tree down. Plastic wedges are strong now adays (true) and I carry plastic (and not steel) wedges with me every day. However, if you hit plastic wedges with a 6 lbs maul, they will break or become damaged. If you have some super strong plastic wedges where you cut wood, more power too you.
I don't know where the stuff about cutting into the steel with your chainsaw comes from. Only an idiot would do that.
If steel/aluminum wedges didn't have a useful application, you wouldn't see them sold just about everywhere that sells plastic wedges.