I find this quite odd. Technically it is quite simple to implement.
I would have designed the scopes to have trigger in and trigger out bnc connectors. Multiple units could be connected in a circular fasion. The software could then set up any channel as the trigger start, force a trigger in the associated unit and measure the delay through the triggers. The software could then re-construct all the channel's data, sequence allowing for delays and display it on screen.
Maybe something to think about at pico?