VK_KHR_present_wait isn't equivalent, because it signals the event on first pixel out, which is too soon.
That's unfortunate, I was thinking VK_KHR_present_wait will solve these problems (which are real WRT games too in some cases) until we have a "direct composition" implementation. Are you sure that this is supposed and actual behaviour?
It's the spec behaviour, actually. I didn't test whether it works in practice, and it's not unlikely that it does work in practice.