In theory you should be able to save 3 frames by consuming the potion when you equip mystletain. Because your cursor is already at the equip menu, it's one less step downwards to get to item use. I tried hexing it in, and it keeps sync after the modified mystletain pause menu, but desyncs after the pause menu in the man-eater room. I have no idea why :(
Scotch Pie
EDIT: looking at the RNG value at 0x2000008, the first discrepancy seems to happen at frame 36699 (corresponding to 36702 in the original), and by frame 36708 the two have diverged completely. This is during the man-eater fight, well beyond the pause screen i hexed. I'm not a TASer by any means and I've never done hexing before, but this is really confusing. Surely if it was going to break, it would have broken before this point?
(Also, by consuming the potion earlier, you hit your HP cap and only gain 84 HP instead of the full 100 HP. I assume this isn't a big deal.)
I'm not making any friends here am I?