Well the topic pretty much explains itself. I mean, how are we supposed to compare the ordnance firepower (namely bombs and rockets) of two different planes without knowing their respective reload time? The Me329 has two SD250 bombs, and the 1099 has four, does this mean the 1099 has twice the firepower? No, because the 1099 takes 90 seconds to reload while the 329 only takes 50.
The same also applies to boost time when comparing the speed of different aircrafts, but that was somewhat less of an issue, as aircrafts from the same tier and same category usually have the same boost duration (with exceptions like soviet and german GAAs).