What i mean is that people would have had to plan and design the idea, then do research into mob behaviour, and none of that could have been done simply, ot would have been a case of trial and error until the fully refined version was finished.Miniguy
that build is not "way too much time on their hands" material.
it is a simple mobgrinder made for the specific purpose of aquiring records using some redstone and a minecart. one could probaby build this in less than 2 hours, or if your name is blinky, less than 5 minutes.