They pay more attention to the other number because that's how the English language works. "9th generation" is a descriptive prefix to the actual CPU model name.

I don't get why not a single brand other than Apple gets product names remotely right. Every time a relative asks me for a laptop recommendation and shows me a list of models I have absolutely no clue what to tell them. All the model numbers look like they came from a password generator and the only discernible difference without hours of looking at spec sheets is the price.