There is another way that's a compromise: give corner cases a home.

In accountancy there is the "General Journal" (https://en.wikipedia.org/wiki/General_journal) - a place to correct of accounting errors, enter adjustments, etc.

The General Journal really only works because accounting entries are immutable: corrections are always new entries. So it's not clear if "give corner cases a home" works everywhere.

But if the principle does work for your use case, it lets the rest of the system be as strict as you like!