Does it really have to add every edited page to the Watchlist? At least set it to expire after the maximum duration (6 months), if it have to.
And it (most likely) adds also pages that wasn't even modified (ex. when all suggested links were incorrect, and there's no entry in page history).
I've been trying to recreate this issue, and failing. Could you please just confirm that this is not a general watchlist setting you have activated, adding pages you edit to the watchlist? See the preference towards the bottom at w:pl:Specjalna:Preferencje#mw-prefsection-watchlist.
I have only two options set, rest options (related to watchlist) is unset:
*Add pages I create and files I upload to my watchlist
*Add new files I upload to my watchlist
I did a Link suggestions test run, and none of the pages were added to watchlist (including one page with all links rejected).
After checking my watchlist for pages that I edited by Link suggestions:
One page without history entry (I remembered that page because two common words were suggested to be linked to two TV series):
https://pl.wikipedia.org/w/index.php?title=Gia_Carangi&offset=&limit=500&action=history
With history entry (one from Aug, rest from Dec 2021):
https://pl.wikipedia.org/w/index.php?title=Wolne_Pa%C5%84stwo_Orania&action=history
https://pl.wikipedia.org/w/index.php?title=Marek_W%C3%B3jcik&action=history
https://pl.wikipedia.org/w/index.php?title=Konstantin_Mamontow&action=history
https://pl.wikipedia.org/w/index.php?title=Jeronimas_Milius&action=history
https://pl.wikipedia.org/w/index.php?title=D%C5%BCummuah&action=history
https://pl.wikipedia.org/w/index.php?title=Daniel_Bryan&action=history
https://pl.wikipedia.org/w/index.php?title=Carlos_Chagas&action=history
Oh, this may have been already fixed - https://phabricator.wikimedia.org/T289547 - or it's just a date coincidence.