The other question people are likely to ask is why, kernel contributions notwithstanding, is Microsoft listed as the publisher of the distro? The short answer: support.
According to Microsoft’s blog post, the FreeBSD Foundation is a community of mutually supportive users, “not a solution provider or an ISV with a support organization.” The kinds of customers who run FreeBSD on Azure want to have service-level agreements of some kind, and the FreeBSD Foundation isn’t in that line of work.
The upshot: If you have problems with FreeBSD on Azure, you can pick up the phone and get Microsoft to help out — but only if you’re running its version of FreeBSD.
To be honest, I don’t see this as a big deal. I’m glad the image is there, but this hardly seems like a landmark change in anything to me.