Huh. That explanation makes a whole bunch of sense.

343i's treatment of the Yonhet was seriously weird. First they hype up the Covenant Fringe like it's going to be a major player in the story, but then they only show one species. That species shows up in, I think, one single issue of Escalation, then Axl starred in Nightfall, then it was mentioned by Cortana in a speech that excluded the Lekgolo and the Drones, and then nothing. Then they get mentioned in... Mythos? One of the books that was recently released?

Eh. Given their weird origins, I vote the Yonhet most likely to get Squatted sometime down the line.