Granted it's a waste if he has to give the panels back.
I was just exaggerating about the "boiling up" 
. He might overcharge them a bit if he's not using them (say leaves it connected on a sunny week but goes on holiday so doesn't use any juice).
200W into 48V is 4.16A and during summer he might get 5 hours of peak power in a 8 hour generating day so that's up to 20.8Ah per day. Call it 16Ah because he's not using a MPPT controller. A 780Ah flooded battery bank might self-discharge by 1% per day which means it needs about 8.6Ah put in (including 10% charge acceptance de-rating) to keep at 100% SoC. So with no other loads, the bank could overcharge by 8Ah per day. It's not going to "boil" for sure but it will lose water faster.
If he's using it every day and having to run a generator as well to charge it then the solar input isn't going to do much, so you're right.
I don't use a charge controller on a spare 110Ah battery that I charge now and then from a spare 40W panel propped up out on the lawn.
