I'm not sure what statistics making a Microsoft account provides an artificial boost to. It's not gonna affect XBL usage, because you're not signing into XBL to play on XBL, you're signing into your Microsoft account to authenticate entry into Minecraft servers. If those servers were running on an Xbox Live network, I still don't see how Microsoft leverages that statistical boost outside of Minecraft discussion.
I'll defer to you guys, though, because I don't know shit about how Microsoft uses their MAU data. Is MS's gaming-centric MAU data influenced by all Microsoft accounts across all services, or just the ones used on Xbox and Windows 10?
Eh not strictly true... You get access to Xbox live friends in their cross platform minecraft
It's definitely Xbox live