Yes, you are right. It’s not a requirement to have a power module for the battery used on the vertical motors. I’ve never actually referred to info it provides in flight. With vertical flight I know the time the battery will last from test flights and that it is good for two take off and landings, if they are quick. My goal with quadplanes is to get up in the air for transition to forward flight quickly and to land quickly. The less time in hover mode the better as far as I’m concerned.
I have the power module connected because I’m doing comparisons of different motors and I like to check the logs for current draw and voltage drop of the batteries. The more data the better.