Gerrit does not send email when a new patchset is created using the web interface. (I was annoyed about occasionally missing notifications for a long time, and I think I finally realized what's causing it.) It sends email only when it is pushed using Git commands.
For example, on https://gerrit.wikimedia.org/r/c/mediawiki/extensions/ConfirmEdit/+/937981, I did not get any emails about patchset 2 being created (by editing patchset 1 in the web interface), but I got an email about the subsequent comment.
Potentially related upstream issue:
- https://issues.gerritcodereview.com/issues/40015612 - Email notification when somebody publishes an edit on a patch set of mine