Part of the series «Have sane defaults, obviously».
There's absolutely no reason to avoid doing this in MediaWiki, and continue hiding such a crucial feature as the watchlist to users who don't know all the inner workings of MediaWiki... except that bug 36316 has not been fixed.
WMF can't always slow down MediaWiki development, though, so if that bug is stuck let's fix MediaWiki and set the old default for Wikimedia projects before upgrading: easy.
- set watchcreations and watchdefault in $wgDefaultUserOptions in DefaultSettings.php;
- don't forget to note this in the release notes files (it affects also old installations upgrading, and all their existing users whatever their preferences).
"Add pages and files I move to my watchlist" and "Add pages and files I delete to my watchlist" would make sense too, but nobody cares: those users and sysops are surely able to do it themselves.
Note: bug 39513 is caused only by that LQT config independently by watchcreations, if my bug report is correct, so that's not a blocker.