I'm actually OK with running into these kind of entries... just that I have a tendency to expect non-standard samples (as in, samples not found in the game) to be thrown into the mix, too (Actually, I've at least partially reverse-engineered a few sound drivers myself... I think of Battle Commander and at least one version of Ocean's sound driver. I almost attempted to reverse engineer Super Mario RPG's because I got so curious... until I realized my mistake. I prefer making my own because I see much larger future potential in doing so, especially when it comes to games. Plus, I can do my own customization.).
For AddmusicK/SMW in particular (well, that and its predecessors, actually), I've found myself getting a bit too bored with the same samples that came with the game (Super Mario World) being used over and over again (I don't have hundreds of these, but I do have one such pack where I believe there isn't any sample swapping involved). Plus, unless it's a more common source (in which I can confirm it's from a SNES game, but there are multiple possible sources), I've got an eagle eye for detecting samples from actual SNES video games (I don't care about this approach, actually, for these songs, as for me, I figure that if it works, then it's fine by me).