`f(++i, ++i)` is/was indeed UB, but the example in munificent's comment was `foo(print(1), print(2))` which as far as I know is not even if both `print` calls read/write the same memory.

(5) in the paragraph I mentioned earlier seems to prevent interleaving of function calls, which admittedly would make the language hard to use. So I think you are right.