The stock chargers in many of the trailers have had float capability for a long time. The gotcha has always been *how* they go into float, not if it's there at all. The process always involves "are we below some magic current?" followed by "have we waited long enough?". You the go into float. If you go above some (possibly different) magic current, you come out of float.
Good luck finding all that info on a typical charger data sheet
If the parasitic draw on your trailer is higher than the "magic current" to go into or come out of float ... you never go into float. If the timer is something like a month and you never wait that long ... you never go into float.
The flip side is, if the magic current limit is set to high, you go into float too soon. The battery is not done charging and you are now in float mode.
If they are going to sell the same charger to somebody with a single 60AH battery and somebody else with a bank of ten 100AH batteries ... somebody is going to get the wrong setting.