I'm not following. Science gives us good guidance on what works well or will let us achieve our goals, all the time. It's basically the whole point of doing it at all.
I took the poster as meaning UX that considers the results of, and perhaps even performs, actual user testing & observation, to decide what works and what doesn't. Like operating system vendors used to. I'll grant that "scientific" UX that's just incompetent (99% of the time) application of "telemetry" and A/B testing is awful. But that—and the other bad kind that's just trend-following, personal preference, and whatever will get the best reaction in a design presentation meeting full of non-experts—aren't what I understood as being advocated.
The good kind performs & pays attention to science.