I just got a Keystep 37. If i route aftertouch to cv, it does not get reset to zero when i release notes. Instead the last value gets held until i play a new note. To lower the AT cv output i need to play a new note, press harder and then softer. So it’s not possible to use it consistently for expression.
Also, you can either have the hold button send a CC sustain message, or have an arp latch. One or the other, or both at the same time but that means when the arp is on, both the notes gets latched and a sustain message is sent.
What i would expect is like on the Keystep pro, hold enabled lets you sustain notes indefinetely, unless the arp is enabled and then it will latch notes.
Otoh, the Keystep 37 does not suffer from stuck notes constantly like the Pro version does.