I see.I've summoned 3 or 4 SBs overall on my account so far, not from x-1 maps but rather 11-4, 12-3, and 12-5, although I haven't ran a lot of x-1 maps to either debunk or validate that.
You're right. I'm not really keen on moving away from 12-5 as my farming stage regardless of SB summon %, probably not anytime soon.