If I follow your argument correctly, it is basically the same argument as "your C compiler is correct, what you've written is invalid and the standard allows undefined behaviour here".
Which may be a technically valid argument against the compiler/database system, but it's not a valid argument for defending the system as a whole: if a standard allows arbitrary execution instead of bailing out on non-standard (ambiguous) input, it is unreliable.
Is variable assignment in c/java/... unreliable? It behaves very similar to what C* does. Concurrent access and modification will produce undefined behaviour if you don't explicitly protect it.
Getting access to things like concurrent locks is HARD to get right. That is why there are so many simple languages that don't let you touch concurrency.
Doesn't mean there is no need for it in the world, and no one should be able to use it.
Which may be a technically valid argument against the compiler/database system, but it's not a valid argument for defending the system as a whole: if a standard allows arbitrary execution instead of bailing out on non-standard (ambiguous) input, it is unreliable.