horizontal splits are very uncommon... seems an unlikely option when it would have been easier just to write the data in the correct place in RAM, especially now we've seen it on multiple games.
this is compensating for something else, almost certainly.
if's probably just a case of 'if (xscrolltval + xdrawpos) > limit then used_yscrollval = yscrollval - 1' or similar instead to compensate for some hardware quirk.
