Anyone...?
If not, I'm going to be forced to guess....

I'm pretty sure the VGI blocks the plant's natural gibbrelins, which controls overall height, but not the branching. Gibbrellins also increase in the tallest shoot on the plant, too. I wouldn't think maturity would be affected unless the plant needs time for healing. There's a Phosphoload 'how-to' page online.

I looked it up. Is this similar to the VGI you are talking about?
InfoSheet-Phosphoload