Charger won't draw more than genny can give him, that's for sure.
When the goal is "real" 100% SOC, the difference between 30A and 45A charging current won't be that significant. Especially if they have a pair of 6V and only have to put 110 AH to get it from 50% to 100%. After a few hours at 30A, battery bank will only need few amps of current. But, hey, - let them go for 1000W, we should keep our Japanese friends happy :)