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.

I've yet to play with FT8. I've had to sell my radio equipment when I became disabled. One day, I'll get back into it again.