Also interesting: the laptop in the slides is a MacBook, not a laptop running Windows. It might look like a generic aluminium device, but see the window decorations...
Plenty of people in Microsoft use open-source tech running on Apple hardware. It's not rare or unexpected anymore in this current decade.
There is a big difference in "using for work" and "using in promotional material"
Why would they go buy a Macbook and put their Microsoft acquisition presentation on it for the subtle PR that they acknowledge Macs exist? How does that make sense? If they were going to put that much effort in, why wouldn't they to full ham and use something running Linux?