Right but clearly 5% is still much closer to the ground than it is to the sky. Not that ground-rocketed makes any more sense because it doesn't.
Skyrocketing in this context is a fast steep rise, moving fast toward the sky; so it's about relative height in a specific timeframe, not absolute height. I mean, nobody would say Windows is skyrocketing, because it already is the sky (here).
Things can skyrocket whilst being relatively small compared to other things.