Core i9 1 CPU maximum frequency...
I believe the CPU frequency is fairly dependent upon the environment, that is, the ambient temperature and humidity. (That is, if you stuck the laptop in the freezer, the achievable CPU frequencies would be higher.) Also, the speed readings depend upon the granularity of the frequency measuring code (i.e., how long the moving average time interval is), especially on the latest 8-th generation Intel CPUs which can alter frequency extremely quickly. I used Intel's own "Intel(R) Power Gadget.app" to record the following CPU frequencies. And finally, the maximum CPU frequency will also depend on the optimization of the running code, with more highly optimized code probably able to achieve higher CPU frequencies. Also, because of the nature of today's CPU architectures, with speculative execution and address caches etc., the CPU frequencies may also vary slightly over time as the CPUs "learn", for lack of a better word, to run the code more efficiently. [One could even write code, not to perform any useful task, but simply to maximize the CPU frequency.]
Running a number crunching program (my own code) on 1 CPU of the 2018 MBP core i9 2.9GHz, I've seen CPU frequencies of 4.55 GHz using the Intel Power Gadget, but no higher. Once again, this doesn't mean that the CPU was not pushed to 4.8 GHz at some point, what it means is that over the time interval employed by the Intel Power Gadget app, the moving average of CPU frequency rose to 4.55 GHz (the mean frequency, in other words, over the measurement time interval).
Running Prime95 on 1 CPU, I've found a maximum Intel Power Gadget speed of 4.47 GHz.
In summary, one must be careful when reporting CPU frequencies to consider both the environmental conditions as well as the granularity of the frequency measurement code (i.e., the moving average time interval length). Just because the maximum measured CPU frequency is less than the specified turbo speed does not mean that the CPU frequency did not achieve the maximum turbo CPU frequency at some point during the time interval.
What do you think?