It was my understanding that the twl4030 capacitor for boost mode was not there (in the schematic at least).
We are missing some capacitor to put TWL4030 GAIA boostmode to work, but N1140 bq24150 USB Bat Charger chip is perfectly suited for that. The i2cset cmd you're asking about does exactly that: enable boost mode (aka supply VBUS) in bq24150