I am also a licensed ham, and you are right. HF digital modes are very low data rate. A low bits/sec data rate because of the limited bandwidth will result in high latency for any nontrivial message length. FT8 is only 6b/sec for comparison. I’m curious to learn more about how they would use the spectrum.
Also a licensed ham here (though no real HF experience). @lchapman has a good point about the latency being only a fifth, but HF is pretty low data rate still. The ionosphere is not ideal, so error correction would need to be put in place, further lowering the datarate. The only thing I can think of is that they would do something with more bandwidth maybe? But why? So some fat cat can trade at just slightly faster than the competition? This seems irresponsible.
