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.
It creates semantic dissonance. There's nothing wrong with saying it doubled to 5% which is much more informative anyway.