The difference is, a petrol machine has the power unit (engine) at the bottom end, with a drive shaft going all the way up to the gearbox by the strimmer head/cutters.
On battery powered, then motor is at the top, directly driving the cutters. The main shaft will only have a couple of wires inside, so a having it as a multi tool doesn't really make sense.
Bare in mind most of the cost is in the batteries, so you could get a couple of bare tools.