Looking at that, it is for the AMPXF addon to fix.
However, there shouldn't exist a scenario where a user/guest would land on such a page.. (unless manually adding ?amp=1
to a 404 page)
Note: I might ofc be wrong 😁
If a user comes in through e.g. Google they will be served the cached AMP page, and at the same time googlebot will recrawl to refresh AMP page content (for next visitor), and it will then notice the 404 and stop showing the search result to other searchers since the page has disappeared..