I mean, he chose them because they already include a camera, mic, battery, gps, and the ability to record and send data to cloud storage without a wifi connection. Yeah, you could individually buy all those components and get them to work, but why bother when you can grab a few $100 phones that do the same thing? Engineering is a much about practicality as it is design and fabrication.
I’m not trying to go up to bat for Mark Rober, I get a little bit of the ick from weaponry videos, too (and the dude clearly doesn’t need my help, anyway). I just think the reaction to him is a bit overblown.