The point of a priority 1 bug is that it must be fixed immediately, possibly justifying a hot fix or dot release all by itself, because:
1) it's a sev 1 bug (security, crashing, data loss) that is actually getting triggered a lot on a live site
2) it's blocking other people's work
I agree that that's a bug that should be fixed before we launch 5.1 but must it be fixed before we take off the code freeze and branch and go alpha?