It's also worth noting that GRX di2 shifters can run XT/XTR di2 2x derailleurs. The standard XT 2x12 setup is a 36/26 chainset with a 10-45 cassette, but I would imagine you can run a range of chainrings and cassettes with this setup. This seems like another possibility (albiet expensive) for very large range gearing with drop-bar shifters.
That said, the need for gearing this low on a drop bar gravel bike seems fairly niche to me. I have a feeling most gravel bike buyers are looking for something closer to a road bike than an MTB, both in terms of gearing and use.