The diff link in the mobile watchlist just shows the page, and not the actual diff.

For example, this link https://en.m.wikipedia.org/w/index.php?title=J._R._R._Tolkien&curid=15872&diff=983880827&oldid=983857258 , which I see in my watchlist in mobile mode, redirects to https://en.m.wikipedia.org/w/index.php?title=Special:MobileDiff/983880827&curid=15872 , and this, in turn, is rendered simply as the article https://en.m.wikipedia.org/wiki/J._R._R._Tolkien .

In the desktop watchlist, the link to the same diff is https://en.wikipedia.org/w/index.php?title=J._R._R._Tolkien&curid=15872&diff=983880827&oldid=983857258&diffmode=source , and it is rendered as I would expect.