Your maths is correct but irrelevant. Your alarmist assertion about when autoland kicks in with firmware 700 is incorrect. But I suppose it is in keeping with this thread...
It is true. Firmware 400 I can run my battery down to 10% before the forced autoland kicks on by default.
In firmware 700 it kicks in at 16%
So you do the math, what is 100% minus 16%?
It is 84% is it not?
I can assure you I am on Firmware 700 and forced Autoland still kicks in at 10% as it has always done.It will add a buffer to the 10% if at altitude. If it actually had changed, don't you think someone else might have noticed and commented?
Here is a flight from a couple of days ago. I never had any critical battery autoland event. I flew around and eventually landed at 12% when it suited me to do so.