It’s going to be pretty common to for a daw/sequencer to ‘re-voice’ mpe notes… basically because it’s necessary if you start editing notes…
e.g.
imagine adding new notes, they have no channel, and the one used would depend upon other active notes etc
also, what if you have use a controller set to 15 voices, but only played up to 4… and then shifted it to a vst the only had 4 voices?
frankly this area is a bit of a mess, always has been …centering around who is responsible for voice allocation?
also lets remember, in non-mpe midi, thats polyphonic… the sound engine is responsible for this.
so natural to feel that should be the case here too!?
as for hapax… squarp have not really followed thru on the mpe side (yet!?)
I did have a long conversation with them, about areas their ‘simplification’ would create potential issues on - and this included using restricted channel numbers for outputs.
though I admit not on input… so that would need to be raised with squarp.
(not recording 15/16… I cannot see them allow arbitrary recording to capture mpe+ data, or enough demand for explicit mpe+ support)
as for recording in daws…
unfortunately many daws are now doing a limited MPE implementation, and explicitly looking for ch press/cc74/pitchbend… and ignoring the mpe specs (which says you can have other voice messages)
perhaps an interesting one to check would be Cubase… although it now has MPE support, for years before, it had multi channel recording (on one track), which was not fixed to the mpe spec… actually I suspect it goes back to the per voice messages they introduced in VST3?
anyway, it then acted like a midi recorder. not sure if re-voiced channels, I suspect it might NOT have.
again, to be clear if testing, Im NOT talking about its mpe mode, which may have been restricted.
(also, this was an older version of cubase, not sure if its changed on the later versions)