That is not a safe assumption. Disney makes more money from more people buying FP. Having more people in FP lines will cause longer standby lines, but that will only further incentive people to buy FP, so it benefits them.
Paid FP inventory might be slightly less than Free FP, but it’s unlikely to be significantly less.
I just don't think this is true. They could sell as many as they want, but if there starts to be significant backups, as was the case with free FP many times, people will feel like they were getting ripped off. Disney has to thread the needle carefully by selling enough meet their goals, while limiting it so that the guests feel like they are getting what they paid for.