I'm not sure if your team is large enough for the following question but: do you find that usage ratios are comparable to general (global) browser share stats?
The product states it's compatible with a bunch of browsers; of course the devs use a mix. That's not interesting.
But like the requisite non-white person in every group photo, Microsoft's choice of browser screenshots most certainly is a conscious decision. For the same reasons. It's not to fake relevancy; it's to signal they're culturally aware.
Truth is, you use what browser you like. On my team (MSFT employee) this is a mixture of Chrome, FF, IE, and Edge, based on personal preference.