Yieks, Guys get it right. The video is very good and the sound guy doing it would agree that your description is really uninformed. This is NOT a video about recording Foley, it's a video about recording sound FX. Go out and borrow or buy a copy of "The Foley Grail" fi you want to know what Foley is about.
The video though is very good and never calls what he is doing Foley because he knows and says he is recording sound FX NOT Foley.
And if you are going to use the word at least spell it correctly. It's Foley, always capitalized (it's a proper name).
The "Wilhelm scream" is actually a bunch of screams by an actor that were recorded for the film "Yellow Sky" in the 50's. The actor managed some particularly agonizing screams and they have been reused countless times in all kinds of films and TV shows. So much so that they are recognizable by many people. There are also a number of designers and editors who have used them as a bit of a signature and sneak them in in one way or another in every project. Ben Burt is probably the most famous of those.
I find it scary when the intro doesn't get it right. Two things off the bat Foley is always capitalized. It's a proper name. Second Foley is NOT sound FX it's actions recorded in sync with picture. While you can in theory record it in your back yard that requires video playback that you can watch and perform the Foley to. What you can record just about anywhere is SFX. The key difference is SFX are recorded wild and later put in sync and Foley is recorded live to picture IN sync.