Your original point still stands. It's possible that the men chosen to do the readings just so happened to be better readers/pitchers than the women, even with the exact same script. It's hard to think of a foolproof way to control for that, other than getting a large enough sample and recruiting both men and women of approximately equal experience. Neither of those is a perfect solution, though.

Theoretically, you'd want some way to have the pitches read with precisely the same cadences and intonations, but have the ability to just swap out a female voice for a male voice. One could imagine a computer program which "female-izes" a man's reading, though I doubt anything like this exists in a form which produces a perfectly realistic sounding female voice.