the principle of charity does actually result in a map shift relative to the default.

What is the default? And is it everyone's default, or only the unenlightened ones', or whose?

This implies that the "default" map is wrong -- correct?

if you have not used the principle of charity in reaching the belief

I don't quite understand that. When I'm reaching a particular belief, I basically do it to the best of my ability -- if I am aware of errors, biases, etc. I will try to correct them. Are you saying that the principle of charity is special in that regard -- that I should apply it anyway even if I don't think it's needed?

An attribution error is an attribution error -- if you recognize it you should fix it, and not apply global corrections regardless.