I'm currently playing an apprentice-level wizard in a GURPS 4/GURPS Dungeon Fantasy/DFRPG hybrid campaign online (campaign has been running since long before DF/DFRPG appeared and has many legacy situations, as well as a few legacy rules in place, but generally bows to official rulings). My character has the Mana Enhancer 2 advantage (consuming almost half his character points), which means in the Normal Mana level of the general campaign area, his effective mana is Very High Mana.
Relevant to this question, on M6 in Very High Mana, "a mage who spends FP to cast a spell on his turn gets those FP back at the beginning of his next turn." This allows even an apprentice with few spells to pull some nice tricks (at the risk of any given casting being his last), but one I've been called on is that apparently, by the strict wording of Very High Mana, this instant recovery of spent FP only applies for casting and not for maintaining a spell.
Thus, if (with an effective mana pool of 11 FP) I cast a radius 5 Create Fire (skill 15 gives -1 FP discount at casting and for maintenance, so casting cost 10 - 1 FP, 5 - 1 FP to maintain), I don't need to roll to remain conscious and on my next turn I'm not fatigued -- but any internally reasonable mechanism by which I would regain my casting FP this way seems as though it should also apply to FP spent to maintain a spell.
It was presented to me as a balancing point for the Mana Enhancer 2 advantage, but to me this seems adequately balanced by the fact that, in Very High Mana, any casting failure is treated as a critical fail, and genuine critical fails are "spectacular disasters." With base skill 15 (very reasonable for an apprentice wizard) and using the "Alternate Magic Rituals" rule from M9 to gain effective skill 16 (with 2 second casting time for most spells), failure will only occur on 17 or 18, and true critical fail only on 18 -- but that's still a crit fail of one kind or the other on one casting in 54, with honest dice, vs. one in 216 for Normal Mana and the same effective skill.
So, tl;dr, is there an official ruling from SJ Games or a line editor (or other rules authority) on whether instant FP recovery in Very High Mana applying only to casting, not maintenance, is an intentional limitation or an omission? And if this differs between standard GURPS and Dungeon Fantasy or DFRPG, which ones are which?