If 'mostly' means over 50% you could call this clear.

Otherwise I don't think this is clear at all.

Otherwise, what is mostly?

Mostly at the outset, or at any given time? Must the project move out when it goes from 49% to 51% AI-assisted code?

"Mostly at any given time?"

Yes, old project with 1M LOC of pre-AI code + 100% AI 100k LOC generated coded for the last three months, is that mostly?