Phil, I imagine they used the 7611 because of cost. The 7622 really could support jumping the truck via the camper batteries.
Why turn it off? Well, scenario I saw often was my dumb alternator pumping up to 90A into the camper batteries on startup, and down to 50A until the batteries were showing 98% SOC on my BMV, at which point I would switch off the connection, and let the solar panels finish the charge process. The Victron MPPT is way smarter than my dumb alternator on the ins/outs of charging the batteries.
Now with LiFePo4, I don't have the 7622 installed, using a Victron Orion 30A charger instead to protect my alternator. I suspect (not tested) that my 200AH BattleBorn battery bank could take all 135A that my dumb alternator could put out, until it burns out or the batteries are full... I am thinking of putting it back in using rando's switch method to enable charging for 30 mins (until I see smoke from the alternator?) for a rapid charge when daylight is not available and I need to top up in an hurry.