Is comparison of shared data thread-safe?

[Nick Treleaven via Digitalmars-d-learn]

With -preview=nosharedaccess, I get:

    int y = 2;
    shared int x = y; // OK
    assert(x == 2); // no error
    y = x; // error

So for the assignment to y, reading x is an error and atomicLoad 
should be used instead. But is it an oversight that reading x in 
the assert is not an error?

I have also found this in a unittest in core.atomic:

        shared(size_t) i;

        atomicOp!"+="(i, cast(size_t) 1);
        assert(i == 1);

Is the assert somehow thread-safe?