Is it a downside? Surely you jest because saying so, imho, is demeaning to Asians. You artificially set a barrier they can't overcome until they turn 40.
What you might have said, or I would say, is that the question is how attracted are you to men who look very young despite being of age and more. If you are not attracted to the same, then it's on you, not the Asian.
I don't think that the Asian in question looks so young as to be mistaken for being underage. But I have seen several Asians in my time...it gives me a frame of reference.