In my opinion, there's very little reason to force 6 voices into 1 screen, and from UI/user's point of view I can see several issues with it: 1) SID1 and SID2 sequence list may utilize different loop points or even play at different speeds, which makes the conjoined "current sequence marker" redundant or at least problematic to display properly, 2) SID1 and SID2 do not share the same filter type/value/envelopes, so the filter behavior between voices might become counter-intuitive for some users, 3) the same applies to ring-modulation/sync links between the voices, 4) small fonts on (yet even smaller) CRT screens might become unreadable, defMON still is a native C64 tracker.
What I am considering instead though is something like a "defMON 1.5", which builds mostly on the good old defMON, but that does some changes that might break backwards compatibility of the tunes. (defMON 2 would do that too anyway). I haven't decided though, so at the moment this is just something that I have been thinking about
Both ways seem like great ideas and I'll try to support them outside of the forums as much as possible.
Is this an actual c64 defmon recording?
If you're asking if the recording comes from real C64 machine then the answer is no. This is Vice 2.4 video-grab utilizing reSID-fp emulation (which I highly recommend), in this case: SID 6581R4AR model (one of many, as they all sound dramatically different).