Can a low side N-channel MOSFET in a DC-DC converter limit inrush current?
This can definitely be done. However, like any low side control, you should only do this if the return of your load is isolated from the ground of the source.

In many electrical and electronic systems, exposed conductors (like shields or chassis) are at ground potential. Thus it's not safe to have two systems (your power supply and load, for example) with different "ground" potentials, because they could easily be shorted together. This, combined with the convention of positive supplies (i.e. systems where ground is the lowest potential) probably explain why it is easier to find high-side inrush control solutions.