I'd sure think any objective interpretation of "defender" would include calvary/tanks, but stranger things have transpired.
That said, if you review my statistics closer to the top of this thread, I can clearly observe when activating/deactivating the museum artifacts with "Defender Spawn Time"...
I think one of the biggest frustrations with the discrepancy between the replay and the reported battle results for the attack is that it seems to mask the incidence of cheating. About 25% of the time I actually watch a replay happen, it reveals that the attacker did something like use 10...
I went through four different "Game Master" support techs on this issue, and there seems to be a very quick instinct to just say things aren't reliable due to known issues and then quickly close conversations. I don't get the sense the support group is there to do much of anything except quickly...
I am experiencing the same issues with Museum reductions in spawn time not working. I have completed Sultan Saladin's capstone, have the Acropolis (-22%), and currently have -30% defender spawn time built up from museum artifacts.
I'd expect to see second-wave spawn times that look like this...