From the discussion above, I guess I am trying to ascertain if the dates labelled differently as 'Last modified' on the profile and the Watchlist 'Edit' column come from the same source.
It is possible, obviously, but that seems to me to be unlikely given the experience that I have had many times over many months of the watchlist edit date being later than the profile's last modified date. In all cases that I have noticed, the profile date has usually been related approximately to the date I last worked on the profile (maybe precisely), and the Watchlist date is related to something that happened later. I have noticed this many times and assumed that the date on the watchlist reflects the many changes, other than my editing work, that are regularly occurring because of other events.
At the moment, the profile date almost immediately reflects this conversation, and that's probably because this conversation is related to that profile, even though I have used it only as an example of many similar experiences. My Watchlist doesn't yet, possibly because it may be updated less frequently.
However, that is opposite to the usual experience where the profile date is much earlier than the Watchlist date.
The profile date usually doesn't change very often. It usually doesn't change until I actually do an edit. In this case, it was on 24 Jul 2019 until we had this conversation.
That very strongly suggests that the dates may come from a different origin.
In any case, it does matter a lot to me. All I am trying to do is say that if they do come from different sources, then it would be much more useful to editors if the Watchlist used the date that appears to reflect the editor's work, so it would be easier to prioritise revision work. Prioritising editing of content I do believe to be important because it does affect the reader's experience.