Exhaustive enums (or type switches) are not a requirement, and are infact harmful - imagine if they add a new kind of syntax node to the language, now your analyzer no longer compiles unless you add a default case - which is very easy to add in C# as well.
Unless you add default... or handle such case, as expected.
Ofc you can use this feature wrong and abuse default case, but in general this is very good since it prevents you about missing places to add handling and screams at you at comp time instead of runtimr
