In reference to #15130 with 3.12 some behaviour of how resulted Reports are showed were changed.
Some users expect that Segements are only applied to user sessions and for example if one URL that is contained in the Segment was part of the session also other data from this sessions as shown, while other users (including myself) think then only the filtered data that is 1:1 defined in the Segment need to be showed.
Right now there is a workarround with disabling this new feature but with Version 4 it probably will be removed. I think before this Version 4 is out we need a new feature that let users define in the Segment definition how the results based on this segment are created (session-based or 1:1) - i don't know whats the best names for this 2 situations.
This also applies to other metrics, not only PageURL.
Thanks for the feature suggestion 👍
Just letting you know we likely won't work on this anytime soon. It would be an entirely new big feature that would also make the UI more complicated etc. At the same time this is rarely needed and users can already achieve it with Custom Reports