Apple’s new top-end MacBook Pro 15-inch, with the optional Core i9 CPU, is markedly slower than last year’s Core i7 design despite fielding two more CPU cores. That’s the result of empirical tests of the system, which show that under full load, Apple’s redesigned MacBook Pro can’t handle the heat its top-end CPU dissipates. It also means Apple has copied one of the worst habits of the boutique PC laptop industry.
Here’s a fact about boutique laptops that doesn’t get nearly enough attention: Generally speaking, the manufacturers of these systems will cheerfully outfit them with CPUs and GPUs that demand more cooling performance than the laptop can provide. As a result, the highest-end systems available often throttle back their own performance to avoid damage.
Apple Can't Handle the Heat: Severe Core i9 Throttling Found on New MacBook Pros - ExtremeTech
Updated article says the i7 version has the same problems, so they must just be using the same chassis as last year's model...It's bad news for AMD as they have a discrete Radeon graphics option as the Macbook Pro line isn't bought by the same sheep which buy the rest of Apple's products, these people will tell Apple where to stick them if they're duff.