The thing is, the player only really has to change his power scales once in the game, and I thought making the message appear only once you fully committed into the UI would make it feel even more annoying, since you'd have to retry from the start everytime. I just find that preventing the UI from being opened at all when you can't switch makes people find it more responsive once they actually can change scales.
Like you said, it's just a small problem, but I thought I'd just share my thought process. ;)
What do you think?
Anyways, thanks for playing! :D