I would suspect that more than 10% of women complain about a male partner being unwilling to perform oral sex on them, or bad at it, even though this might be very important for them and the main way they can orgasm. Men, too, complain about women’s ability or receptiveness to things they need for satisfying sex.
You can't easily tell whether a car will get better or worse the more you drive it, but you can tell when a car is immediately fun to drive. Start with the car that's fun to drive and hope it gets better (with proper care and maintenance) not worse.
My broad point was that it's not universal. And for a lot of people "sexual chemistry" is something they want to evaluate from the very beginning. Even they will probably admit that it takes more than 1 or 2 attempts to validate.
I'm assuming it doesn't mean being capable of basic sexual activity, because that seems like a given for 90% of potential couples. I.e., not something you'd really need to "test".
And if it means "capable of giving each other a really enjoyable sexual experience", I wouldn't think that's something you can falsify in just 1-2 dates. Because there's a learning curve, and that takes (among other things) time and practice.