I wondered about the others being that badly gunked, but since the drivers front is almost directly below the MC, I thought it was more likely to have more. And it didn't pull to the right before rebuilding the MC.
But it's probably a good idea to check the other front one at some point.

I could have some air since I flushed the whole system.... I may drive it for a while, then re-bleed.

There is one place that you have not looked, and it is there - only there - that you shall find the master.