I had mixed feelings the first time I saw that shipping back in 2014. I don't remember the name of the artist, but he made two types of Twisombra fanart: The NSFW content and a what-if scenario where Sombra and Twilight are dating. The artist is incredibly talented, but he makes some NSFW furry content, and I don't like that side of the Internet.
The fact that it's fan-content is enough reason for me to not worry too much about it. It's not supposed to be canon.