Muscle memory is a real thing, and quite important for many. When you think about it, the difference in scale length between an SG and a Strat is only 3/4". Spread that over 22 or so frets, and you're talking about differences in reach from 1 fret to the next or several frets up gets pretty small. Measured in thousandths, really. So, how does hand size enter into it? The differences get even smaller, the higher up scale you go. But, if you're not accustomed to placing your fingers very deliberately and instead rely on muscle memory, you'll start fat-fingering notes as if you've not played in a year or more. I know some years back I used to be able to cover Satriani tunes pretty well, unless I didn't have MY guitar. Then, fuhgeddaboudit. Embarassingly sloppy. Miss half the notes.