I suspect it's passive charging, but unlike MG which balances when the battery hits 100% SoC the BYD starts balancing at 8x% or 9x% the recommendation of charging to 100% once a week hints at passive balancing.
It would be good to know.
Incidentally, I fitted 2 of those watt meters in 2 houses we built, one of them still works, the other flashes on and off. That's after 6 years, they are the DC type sourced on AliExpress. I wired all the lighting circuits up for 24v DC, even table lights which used XLR wall sockets. In the event of a powercut a contactor trips over to batteries. One of those houses was sold, the other I rent out and it has 4 of 12v Lithium motorbike batteries (built in BMS) which will power the lights for a few hours.