[buran77]

The CPU may not be able to scale up the frequency to "100%" at that time due to factors that cannot be overridden, like a high-temp situation.

The problem is what is 100% when CPUs have gotten so complex around the frequency. What's the absolute reference, the base frequency, the single core turbo, the multi core turbo, overclock, AVX?

For batteries you usually get 2 estimates, a capacity percentage of the total practically possible, and one for how much usage you can get out of that based on recent or estimated usage.