Then you will have the same discussion why it is not the other way around.
In server environments i prefer the output in MB inside the details. In some network environments (WAN) it is easier to have Mbit. As every time - it depends on your use case and the possibility to switch between booth are the important thing. The Perf-o-Meter has the problem that it not knows from the rules you defined for the details output as it receives every time the same data.