I beg to differ. Each cell in a lipo is 3.7 volts. Esc' cut off at a safe voltage of 3.0 per cell. The Mavic battery I believe is 3 cells or 11.1 volts. It has built in technology to monitor all three cell voltage as discharged and shut down the quad before cell voltage goes below 3.0 for each cell or 9 v total. Anything below 3 volts will cause the cells to swell and the potential for fire exists. Same is true if you store a fully charged battery. DJI has built in technology to slowly dishcharge batteries when stored. Lipos operate at a range of 3.0-3.7 volts. Less that one volt range. Under normal use nobody will notice .7 drop in power. It isn't nicad or nimh technology. When you run two batteries in parallel you are using 6 total cells (3 per lipo battery) to power the esc to 11.1 volts but with more capacity Basic generic 3cell lipo batteries are just 3 cells wired in series to get to 11.1 volts. When discharged they can discharge at different rates and allow a cell to drop below 3 volts. As long as the quad esc still senses 9v it isn't going to shut down. This could run one of the six cells way below 3v. You also have to balance charge them do you don't over charge one cell. Good chargers monitor each cell as charging and keeps all cells equal.
I have plenty experience with nimh, nicad, lipo, life batteries in RC for the past 15 years. I have seen numerous lipo fires every year. Just google lipo fire.