Sort of. The trinity is a confusing concept as taught by mainstream Christians: three in one in three. But the God of the Old Testament is the Father, not the Son, IIRC.

I’m an exmo, so I’m well aware of what Mormon means. Including that it was widely accepted as an informal demonym for many years by LDS church leaders, and only recently became officially anathema. The reasoning presented for the change has not been terribly sound, I’m afraid, and I wouldn’t be surprised if a future prophet reversed it, as other decisions have been reversed.