Why is exit/die without arguments pure?

[kkmuffme]

#6188 changed that exit with arguments is impure, however I think all calls to exit/die should be impure:

https://psalm.dev/articles/immutability-and-beyond

A pure function is one whose output is completely deterministic given its input, and which has no side effects

Exiting has side-effects - it will call the functions registered with register_shutdown_function. (and if you call this function again inside of a shutdown function, it will actually exit and not trigger the shutdown functions again).
Doesn't sound very pure to me, does it?