Triac can only do leading edge, since it uses the next waveform zero crossing as an auto-shutoff signal (that’s my understanding). MOSFETs can do whatever you want, I think…
Edit: does anyone know if a MOSFET trailing edge requires a neutral? Maybe this is why Inovelli ended up with a leading-edge configuration… I would happily forgo the non-neutral option to get trailing edge dimming. Looks like hardware changes are required to swap between the two, though, so with the current switches we’re stuck with leading-edge. Guess I’ll have to do some research on replacement LEDs that will work with this type of dimmer. Disappointing, but I understand not wanting to break out a separate SKU for non-neutral folks.