Looks reasonable for light loads/audax kit, but has the same issue with seatpost attachment - not recumbent friendly
Lots of things are never going to be recumbent-friendly on this basis; it's like a more extreme version of them not being short-rider-friendly.
TBH, recumbent luggage tends to gravitate to one of:
1) Full touring pannier setup, often involving bike-specific luggage racks, on bikes that are never going to be lightweight.
2) Banananananana or seat-back bags.
3) Rigid aerodynamic tailboxes in various sizes.
4) Lightweight racks mounted to the seat with very limited load ratings (eg. Fujin day rack.)
I think the "enough room for a toolkit, sandwiches and a layer of warm clothing" level luggage is well served for most bikes by one of these, unless you've already filled the back of the seat with bottle cages or batteries or something.
I think a carbon fibre tailbox is the recumbent spiritual equivalent of the TailFin...