The closest I came to trying a break in was to push one tooth all the way into the chain and pull it out 200 times. It still is hard to push in, and the chain still hangs by that tooth.

After snapping additional pictures that Shimano is asking me for, I took the pulley off and made some measurements.

A Starrett 0 to 1" micrometer caliper (mechanical, reads to 0.0001") gave me an average thickness of 0.08727," that being an average over 11 teeth.
Same caliper gave me an average tooth thickness (13 teeth) of 0.08344" for the guide pulley on a 12 speed SLX derailleur on another bike.

I don't have a set of gauges to closely measure the spacing between the inner plates of my chain. I do have a set of drill bits whose claimed diameters line up well with my micrometer's readings.
The round shank of a 3/32" drill bit will not enter between two of my chain's inner plates.
The round shank of a 5/64" drill bit will.

My measurements on the chain are consistent with what I would expect for an 11-speed chain. The spacing between the inner plates on a 9-, 10-, 11-, or 12-speed chain is supposed to be 11/128", which is halfway between 5/64" and 3/32" I think it (and the other brand new 11-speed chain I have) is an 11-speed chain of correct dimensions.

Note that 11/128 = 0.0859375

I would expect, and I can confirm that my 12-speed guide pulley (0.0834" thick) functions with these 11-speed chains and that the guide pulley that came on this Shimano warranty-replacement 11-speed derailleur (0.0873" thick) is too thick and does not function with 11-speed chain. It only squishes in there because it is plastic, but the fit is too tight.

I did take a close look at my 105 guide pulley, and it does say "G Pulley" on it, but there are no direction arrows. According to Shimano, the guide pulleys on Ultegra and Dura Ace derailleurs are directional, but the guide pulley on a 105 is not.

My Ultegra replacement pulleys are supposed to be here Thursday. I will measure them, try them on this derailleur, and post an update.