>(There is one notable instance where Apple embraced enterprise, and that was when Apple added Exchange support in iPhone OS and admittedly, this was a huge deal and was ultimately a fatal blow to Blackberry. But it’s the exception that almost proves the rule. Apple added support for Exchange but left it up to others to figure out the broader MDM situations.)

Yep. There have been a couple of specific things. Exchange and now MDM profiles. Probably a few others. But minor tweaks to remove major enterprise blockers. Small investments to remove complete showstoppers is just common sense.

>Apple hasn’t offered some sort of build/test service themselves and integrated it into TestFlight

Seems pretty logical. Who knows? It's certainly the trend with container platforms generally.