Well, while waiting for a response to my initial inquiry I went ahead and started working on the other caliper. And in doing so I found the problem with the first one. The rebuilder put the retaining rings in upside down. The lips on those rings are at the top, not the bottom where they're supposed to be. That obviously inhibits the pads from opening as they should.

I don't think I can slide the rings around to their correct positions. I have another rebuilt caliper for that side so I'm going to put that one on and just have the store exchange the one that was assembled wrong.