If I cut each arm of a Y off and root them, then those rooted limbs will not bloom till they form their own Ys. Is that correct? If that is correct, why is that?

I've had long cuttings from above a Y make roots and then bloom in water. So no, not necessarily having to grow enough to make another Y. Those cuttings immediately branched, made a short, shrubby plant and kept on blooming once I potted them up, too.

I don't know why. (this is getting confusing) Something about the maturity or size of the stems, maybe?

Thanks for the response.