Yup, I reckon a 4 wheel Isetta would have lifted a wheel a few inches but not as much as that one.
Single-front wheel cars are most unstable when braking while cornering, and the momentum throws the weight "diagonally" to left or right of the wheel and the car tips over at the front. With a rear single braking in a corner is safer, and as this is the commonest and most potentially dangerous emergency manoever having 2 front wheels is that little bit safer, but the drawback is that heavy acceleration while cornering can lead to the inertial force going diagonally over the back wheel and making a front wheel lift, as on this clip. The closer spacing of Heinkel-Trojan rear wheels will only be very slightly better than one wheel, but the Isetta's greater rear wheel spacing and heavier weight would be better.