Running a smart charger off an inverter is better because the constant amps in the bulk stage beat the tapering amps of the jumper cables by a mile. If the charger amps are higher or equal to the jumper's initially.
It is true you can use a bigger amp charger with a bigger watt inverter, but you hit the wall with what the truck's alternator can do to support its battery with that battery being sucked down by the inverter.
What happens is at some higher amps draw from the inverter, the alternator cannot keep up, and your truck's battery voltage as seen on the dash voltage gauge, starts to slide off and down to the left. That is the wall.
Just where this will happen depends on your truck design. I found with my truck I can run about 55 amps of charger with a 2000w inverter clamped to the battery, but that is about it. ( That was with an alternator that was getting old and later needed replacing. I have not tried it with the replacement alternator to see if it can do better)
I have actually done it a few years ago, with a 35 amp charger and a 1000w inverter, idling the truck for an hour with no issues. (Gas truck)
