And I am similarly baffled by your inability to see that the inability to change Powers is a limit on the flexibility spent on that particular amount of Refresh.
I don't think "the inability to change Powers" actually exists.
And even if I did, balancing characters by making different characters overpowered in different sessions is a terrible idea.
As for A Few Seconds Ahead, I don't think it's nearly so imbalanced as you're making out, Sancta--it's only really a benefit for a character who already has high Lore, and it's not even a boost. A character with high Athletics is better off investing in a speed power or something that can boost the roll past the skill cap. It's really mainly a benefit to a character who hasn't invested in physical skills much.
It's not that impressive on any particular character.
But on essentially any character without solid defences, it's good enough that not buying it (or a similar Power for another Skill) would be foolish.
Suppose you want to make a powerful old wizard who isn't physically gifted or a skilled crafter. Then you have a choice between
a) bending your concept to let you take A Few Seconds Ahead
and
b) being weaker than you could be
which is a terrible choice.
You shouldn't make people choose between power and story. That's why balance is important.
(The same rough argument applies to physical defence stunts, incidentally.)