AMD used to give decently accurate TDP, but Intel started giving unrealistically optimistic TDP ratings, so AMD joined the game. Their TDP is more of an aspiration than a reality (ironically, Intel seems to have gotten more accurate with their new base and turbo power ratings).

9700x runs 100MHz higher on the same process as the 7700x. If they are actually running at full speed, I don't see how 9700x could possibly be using less power with more transistors at a higher frequency. They could get lower power for the same performance level though if they were being more aggressive about ramping down the frequency (but it's a desktop chip, so why would they?).