Level 11 Uncut Skill Gems drop when?

EDIT: I am farming in Act 3 btw...

EDIT to the EDIT: I found a level 11 uncut gem - quest reward from Act 3.

I am level 42 and trying to unlock a level 11 uncut skill gem to switch to a cold build (comet). Only thing dropping for me are level 10's...

I have noticed a trend, do I have to be two levels above the skill I wish to unlock for those level of uncut skill gems to drop?

What is everyone else experiencing/noticing?

Thanks

Also drops in Cruel act 1, Grellwood for me
I received one from Brambleghast boss.

Thank you so much for Act1 Cruel Grellwood tip.
Just found spirit gem11 there being at lv90.