Just noticed this, and verified the behavior with a friend who also has a Tetrapad.
When in combo mode, setting a column to switches works as expected in latched mode. I am able to turn the top and bottom switches on and off freely. In momentary mode, I am only able to trigger either/or top or bottom at a time. Trying to push and hold on both switches doesn’t work – I only get a gate from the switch pushed first.
Did a search here and in the manual but didn’t see any mention of this. Sorry if I missed it somewhere.