Working from the expressed purpose of these changes being 'power balancing', the question becomes one of when, and at what rate, powers become undesirably unbalanced relative to stunts.
In my estimation, they do not begin to become notably unbalanced until refinement is available in meaningful quantities, commonly around submerged.
If someone is of the opinion that this imbalance occurs sooner, or perceives as much in their game, bumping up the timetable by a step or two would be a simple adaptation.