[malpighien]

In this case I believe it is more an issue coming from the authors of that particular article. They probably used some bibliography software that recorded the sci-hub as the address for some articles cited, although published articles are peer reviewed people rarely scrutinizes all aspects of an article that finely to pick such issues.

[meristem]

Some citation formats require the URL if an article came from an online source and the date when it was fetched.

[KONAir]

But Doi with publication date alone should be enough as the url and fetch date?

Though sometimes different faculties in same campus have their own absurd formatting rules...