That’s really strange. I tried to open that list with more than 181.000 items and I get a gateway time-out error. I assume not even the user who owns the account uses the list, but the tool generating it is behaving inappropriately / unexpectedly.
These big lists are before we enforced the limits. They aren’t even usable at such a large size like you said, which is why we put more sane limits to allow list pages to load correctly.