Where did you see it? A URL as reference would be nice, thanks.
There was already a similar request for the UFX III, which incorporated the converters from the ADI-2 Pro FS, supporting various A/D and D/A filters. By now, this likely also applies to the UFX II and, I believe, the 802 FS.
At that time, the reasoning given was to ensure that audio material is processed with the filter that alters the audio signal the least (in terms of frequency response, etc.).
Therefore, I am surprised that this capability is now being considered for a "standard" AD/DA converter as M-1620.
I can understand it with the ADI-2, as its product positioning suggests there are additional use cases where the ability to switch D/A filters plays a role.
If this is indeed the case, then I see no reason to allow it for an M-1620 but prohibit it for a UFX III.
After all, the M-1620 is an expansion unit for UFX II, UFX III.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14