When encountering an edit conflict in the ProofreadPage's page namespace there's an erroneously identified change in the page footer.
The old interface didn't identify any such change for a similar edit:
I assume that this comes from the serialization of the texts that are feed into the conflict. Note, that in the core conflict solving UI this is also visible by looking at the contents of the textareas that show your (below) and the other (above) edit.
See also investigation in T165134: Investigate changes needed for Page namespace on Wikisource