Should I be worried if the newest Macbook Pro specs are lower than my older Macbook Pro spec?

I just went to Apple's website (July 2019) to find the maximum processor spec of a 15-inch Macbook Pro to be: 2.4GHz 8‑core 9th‑generation Intel Core i9 processor, Turbo Boost up to 5.0GHz However, my Macbook Pro (15-inch, 2018) has a processor spec of 2.9 GHz Intel Core i9. *Update:* After reading the answer where **six** cores is important, I found the more official spec from Apple : 2.9GHz 6-core Intel Core i9, Turbo Boost up to 4.8GHz Why has the processor speed gone down? Does it have anything to do with the heat problems I heard about in 2018?