Are you claiming that microsoft counts "outlook daily active users" as "teams daily active users"? Cause the article specifies "daily active users", not "signed up" or anything like that.

They’re rebranding Skype for business as teams meetings, and pretty soon anyone who uses Office 365 for video calls for meetings will end up being counted as a teams user (even if they don’t sign in to teams or ever look at chat).

This isn’t too far off, although it’s new enough I doubt it has a massive impact on the 13m number.

That's not how it works.

That's not how it works to a reasonable person, but marketers can count however best suits them.

As long as they don't mind fighting with the SEC, sure.

As a former MSFT employee (on Azure), Teams daily active users are counted even when someone on Outlook hosts a meeting, which is automatically converted into a Teams meeting link. Therefore, unless an enterprise is still sticking with Skype, Teams users will automatically get trickled in from Outlook.

That would only be if they hosted an online meeting (an audio or video conference), not for any outlook meeting (i.e. a meeting booked with outlook doing scheduling, but meeting happening in a good old meeting room). And that is then comparable to slack video conferencing, so probably a fair comparison.