It talked about this in the article: "Probably the most distinctive part of SCUMM was that it was multi-tasking. This meant that multiple scripts could effectively run simultaneously. You might create a clock on the wall in Zak McKracken’s office and have it animate. [...] The script would simply command the actor to walk, and then issue a “wait-for actor” command which put the script to sleep until the actor had arrived or was facing the right direction. This allowed you to write your scripts in a very linear fashion reflecting the series of steps that you wanted the actor to follow."