It wasn't an MS product, or supported, and they still took the time to help. I'd be surprised if one didn't find similar responsiveness from at least some of the o365 developers. More often than not, something is "unsupported" not because it doesn't or shouldn't work, but because it doesn't have the dedicated testing resources and in case there is an edge case bug that would be excessively costly to fix (ex: dealing with stupid flexbox issues with the current version of Safari on mac).
In any case, it doesn't matter, the response was a bad, canned response that doesn't take into account the troubleshooting the person reporting it already did.
"Supported" in this context is clearly "we want more money from your despite you already having paid the agreed amount for this product".
[1] https://www.reddit.com/r/linux/comments/60nj67/office_365_on...