I work for a large organization and make and manage personal programs all the time with absolutely no relationship to or input from my parent organization. Occasionally I am allowed put them on the Org's Github if they're useful and relevant to the mission. It's a cool little perk because it can give personal projects more visibility.

I'm not saying it's not suspicious (I don't think it is though), but I don't think that a Microsoft employee creating their own plugin, even under Microsoft's Github, makes it suspicious.