Testing in Werebear and Spriggan forms. 5/6 in Regrowth. Expected result is gaining 25 mana instantly while leaving form, and 25% mana regen. Neither is happening in either case of leaving form by running out of mana, or manually returning to human form.
Testing by entering form in end of time, draining as much mana as possible, making note of current mana, then either manually returning to human or just running out of mana.
In both forms returning to human manually grants absolutely nothing. Returning by running out of mana in both cases returns the expected 50 mana, but no extra benefit from the points in regrowth.