Why assume it’s forgotten ? I strongly doubt that
You’re comparing a synth mode with a sequencer box
The arp can also be played live and it’s real easy to sequence a sole infinite trig and vary the arp notes using grid mode edits so you can fly hands free
They’re two different beasts, having a latching mode causes all sorts of conflicts for a sequencer that may be easy to workaround but why work around them … you just approach it in a different way
i don’t see this appearing on an OS update tbh but i’m not saying such a way of working isn’t useful - i just don’t agree it’s an omission and the ux won’t be compromised by layering on added secondary functionality
as for why the CC for sustain was overlooked i’m not so sure, again probably linked to messy interactions with the step sequencer way of recording