The burp each minute is likely for the charger to better check the lipo condition, see how it’s responding for safety, and take internal resistance measurements. Good stuff in my opinion.

In parallel there are pairs (or more) of cells at the same voltage. Probably best to occasionally check the individual cell voltages of each pack by itself before charging to keep tabs on each packs condition. As long as they are all similar all’s good, if you see issues of cell balance while parallel charging it takes individual pack measurements to determine which pack is letting the team down.