Given how slow it is, I'd probably just do a 3 ton Foot Bay for the SW Era.
For a true IFV, I´d probably agree with you. But given the disparity in cost and capability between the vehicle and its passengers, realistically the infantry is there to protect the vehicle against infantry in close-quarters environments such as cities, not the other way around (i.e. the vehicle is there to protect the infantry against vehicles), so you´d want infantry that can keep up (at least on a tactical level, see below) with the vehicle.
As noted, everything else is equal/faster than its ponderous 2/3 profile.
Motorized platoons, yes. But jump platoons have a ground speed of 1/1.
I always operate under the assumption that all units can only use walk/cruise speed when moving strategically - running or jumping is just too taxing, and too likely to lead to accidents.
On the tactical scale, with battles that are over in minutes, we can ignore the miniscule risk of some minor slip of attention leads to a mech tripping and falling, or to a jump trooper twisting their ankle while landing, or something like that.
But for strategic movement, where you´d run or jump not 5-10 rounds in a row, but several
thousand rounds in a row, that risk adds up, to the point that it´s just not worth it except under the most extreme of emergencies.
And even discounting that, using APCs allows the infantry to arrive at the battlefield reasonably fresh, as opposed to exhausted from hours of non-stop jumping.
