C enum values are convertible from int; C++ enum values aren't. This is one of the biggest differences in fairly idiomatic C code and has been the case for a very long time (i.e. not dependent on newer C features not being in C++).

    #include <stdio.h>
    
    typedef enum EFoo {
        FOO_A = 1,
        FOO_B = 2
    } TFoo;
    
    int main()
    {
        TFoo foo = FOO_A | FOO_B;
        printf("foo = %d\n", foo);
    }

This compiles in C but not C++.