We know for a fact rules are changing. Do we expect those rules changes to be issued as errata for the existing books? If not, then it's not the same edition and it's an edition change, even if it's just an "update" such as 3e to 3.5.
We've seen this. Tritions, for example, gained Darkvision in a later book. All of the (multiple) previous sources that had them received errata. This is a single edition.
However, starting with MP:MoM, Wizards of the Coast has stopped issuing errata for existing products changed. So I would not expect OneD&D rules changes to be reflected as errata in the earlier books.
Two sets of rules that while perhaps mathematically similar do conflict with each other at points? Not the same edition.
If I can take my completely-up-to-date 2014!PHB and another person at that table takes their completely-up-to-day 2024!PHB and we both have different rules for the Hide action such that the DM or table needs to decided which edition's rules are in force, it's different editions.
Again, this is all based on if they issue errata, and that they will likely continue the trend of not. If they do issue errata, then all of the rule books say the same thing and it's one edition.
Any arguments about backward compatibility or 2014 & 2024 characters sitting at the same table, while valid, are orthogonal to this. Are the rules the same? is a criteria that can not be ignored in determing if things are the same or different.