I don't have often a thick bark, and nothing near what you have on the giants. But I had a peek on it on different occasions.
Clear view on the real wood is a good one for precise cuts, especially with fluffy bark. Same for the trunk covered by a mess of ivy. Just to see what I'm doing.
Thick bark means less reach for the actual cutting. It reduces the lifting potential for the wedges too and can make the wedges hard to set in (spitting out the stacked wedges for exemple).
I remove the loose bark every time, even if thin, because the gap between the wood and the bark ends filled with crap by some of the many small critters near the ground. Ants are masters for that, earht worms too.
Alaping the stump is very common but most of the time I manage it by circling around the stump with only the pulling chain getting out of the bark (after boring in the cleanest area). Ivy is completly removed though, because there's dirt trapped between the ivy's sprouts and the bark. The need to remove the bark on the real dirty ones is rare enougth, like the trees in a pile of rubble or in the bare dird of a flower bed.