[suuuuuuuu]

I think it's just wrong. Related, linked recently here: https://dwest.web.illinois.edu/grammar.html

The authors are biologists, so I suspect they're not particularly versed in mathematical writing (and that McCarthy was not likely providing them much advice on it).

[abdullahkhalids]

The link is a pretty great. A bit long though. Not sure if I can get my charges to read it all and apply it to their writing.