I happen to have a ML10X here and I did the frequency response measurement yesterday. I initially didn't want to post it, because I think it's bad business practice to bash a competitor (more like a David/Goliath situation, though). Anyway, we now have a statement of Morningstar that the ML10X doesn't have a flat frequency response as well as a measurement of another user, so I guess it's ok to complete the picture with measurements with different input impedances, to show that this isn't the issue here.
This is the ML10X with line level:
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This is the ML10X with instrument level:
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Besides the 6dB boost of my audio interface there is no difference. This shows that while the low cut on the HYDRA4X happens with the output stage interacting with the following input, the low cut in the ML10X happens on a deeper level. This corresponds with the statement of Morningstar that it is because of the buffer design around the crosspoint switch.
Please note that I have all the love and respect for Morningstar. I use a MC6 on my board and the ML10X is an outstanding piece of gear. I also recommend Morningstar products to every client that is asking for advice on MIDI controllers. They did groundbreaking work in the field of MIDI for guitar and bass players and without them Oscillator Devices probably wouldn't exist.