You've got it backwards. No I'm not jewish but I can read.
"The Gemara asks: What does it mean that the Torah does not deem a younger boy to be like an older boy? Rav says: It means that the Torah does not deem the intercourse of one who is less than nine years old to be like the intercourse of one who is at least nine years old, as for a male’s act of intercourse to have the legal status of full-fledged intercourse the minimum age is nine years."
Deals were sealed by marriage/intercourse. It means it didn't count for a boy under 9 and he would still be considered a virgin. So for instance an 8 year old boy couldn't be married off and legally consumate it.
It's talking about the legal standing of the kid, not the adult they have sex with.
Still fucked up 9 years old were considered old enough though.