This kind of flexibility is a purely historical thing.

On modern computers, it is impossible to write correct C programs that are agnostic about the true size in bits of the "flexible" types char, short, int, long and long long.

If your program must depend on assumptions about the size in bits of the integer types, those assumptions must be made explicit, by using types like int16_t, int32_t etc.

Writing correct programs that are agnostic about the integer sizes is possible only in programming languages that allow the programmer to install an integer overflow handler even if the CPU does not generate a hardware exception for that, in which case the compiler must insert appropriate overflow checking instructions that would invoke the installed handler when necessary.

This problem did not exist on old computers, where there were hardware exceptions for integer overflows, so even in C you could install a signal handler for SIGFPE, which would also be invoked by integer overflows.