Earlier quoted context omitted.
How is this significantly different than placing a video camera in front of a screen? Yt-dL is surely nicer and more convenient, but from an evidence standpoint, a one time $500 (to go wild) setup should have you covered, no? (Mourning the loss of ytdl myself but trying to be realistic)
I think this is absolutely reasonable question. Filming the screen, means that in order to fake it, you have to setup something that routes youtube.com to your own fake version of youtube, before filming. To me, that sounds much harder than say "this file was downloaded from here on that date"
I kind of expect a serious investigator to archive these materials just for the sake of it. I don't expect them to make it harder on themselves for no good reason.