The chance that it might liquefy is a good point. Soylent powder has the oil/fat bound to the dry compounds which separate when wet. At least that’s my basic understanding of how it works along with my basic ability to explain it offhand. Lots of pressure may work as an oil press and simply squeeze out the oil/fat from the powder. I don’t know about binding powders under pressure but I think a think an oily greasy powder probably would bind fine, but you’d lose a good portion of nutrition via not only the squeezed out oil/fat itself, but also nutrients that would dissolve into the oil/fat when that portion of it liquefies.
Edit: I suppose you could technically put pressed oil into gel capsules, but you’d probably want to collect the oil/fat first using machinery designed to do that, so although probably possible, it sounds like a complicated manufacturing process. But if somebody already has a tablet pill press, give it a shot! It may gunk it up, but I’m at least mildly interested to hear what would actually happen if you tried.