STB only works with something like MHRB, that has very little in the way of fats and just dumps DMT at the drop of a hat. If you're working with oily material, you need to defat it first (so acidify, do a pull with a non-polar solvent that just gets crap, then basify, pull again with non-polar to get your clean DMT). It's not really about different alkaloids, if you've got NMT or 5-MeO-DMT in there it's probably beyond the scope of this kind of kitchen chemistry to isolate those. This is just about producing a nice, clean alkaloid extract. You're right, though, these techniques are broadly applicable to a wide range of plant materials, I do STB just the same on Peruvian Torch, pull with xylene, then salt the mescaline out with aqueous HCl. STB is simple, but limited, with A/B extraction, and defatting, you should really be able to get any basic amine out of any mixture of undesirable shit.
Psych, I'm pretty sure that DMT is present as a salt in the plant matter, so you'd end up defatting the leaf with DMT still in it (which is probably the more convenient thing). I imagine you'd be able to go STB with it from that stage if you saw fit. It seems like an expensive way to do it, though, you'd achieve much the same thing if you just dumped some toluene or xylene or something in at your acid stage and then pulled and discarded it.