From User:Floflo:

I notice that the feature also works on my watchlist. It is a little bit annoying because I move my cursor a lot on my watchlist to check several edits, so many hovercards appear for nothing. Moreover, as far as I'm concerned it is not useful on watchlists because I already know all articles I watch...
I don't know if many people asked for Hovercards in watchlists, but for me this is not useful, and even annoying on the long-term.

https://www.mediawiki.org/wiki/Topic:Tp17gv6ep1kr2gol

I'm not sure this is intended or if it has been discussed. Perhaps worth reviewing this Special: page and others.

Addendum: NavPopups do appear on Special: pages, including the watchlist.