User blog comment:B214/Don't ask about season 4/@comment-26821288-20161113192209/@comment-3965848-20161113214705

And the amount of budget they have, although they could make the GvS RG into an OVA, but events from V7 might be the hardest to fix.

Honestly it was kinda unnecessary to alternate story that much, I mean you see other anime go for 3 vols into 1 season and still stick to the original source material.