I don't think that's what descriptive fair use means.

> Descriptive Fair Use: Found at 15 U.S.C. § 1115(b)(4), the descriptive fair use defense protects your ability to use ordinary words to describe your own goods or services, even if those words happen to be part of someone's trademark.

https://www.dmlp.org/legal-guide/using-trademarks-others

Since the Windows Subsystem for Android actually runs Android, "Windows Subsystem for Android" is a product name and not just a description, and "Android" isn't a generic descriptive term in this context, it seems to me that Microsoft is using Google's Android trademark in a way that isn't protected as fair use.