The rest is very accurate, presumably he didn't have a true WEco #500 and found the cheapest #500 set in good shape he could.

AT&T owned 22 operating companies that did local phone service throughout the US, they served at least 2/3-3/4 or all US telephone subscribers. Most major cities were served by Bell, the only major city not was LA which was served by General Telephone(GTE).  Automatic-Electric, Kellogg, Stromberg-Carlson, and ITT made #500 set phones were virtually identical to AT&T's Western Electric made phones, they licensed the design out, presumably. 

Old AT&T's structure was as follows, AT&T owned 22 local phone companies such as C&P Telephone, Pacific Bell, Illinois Bell, and New York Telephone, these companies were who you paid your local phone bill to and who owned the equipment and building that gave you dial tone. AT&T also owned AT&T Long Lines, the long distance provider which owned major tandem switching machines throughout the US such as 4A Toll Crossbar switches and #1 Crossbar Tandems, they also owned coaxial cables throughout the US and many microwave radio relay stations that operated on L-carrier and microwave carrier respectively. AT&T also owned their equipment supplier, Western Electric, that made everything from undersea cables to 4A Toll machines and your(not technically yours, it was leased) #500 set. AT&T then owned a research laboratory, Bell Labs, that invented many things we still rely on today and many elements of modern technology is based on such as the transistor, UNIX operating system, 4ESS toll office, 4x the capacity of the electro-mechanical 4As.

We could certainly pick his post apart just like he's done to the various dubbings, but it was still interesting.  A little OCD for me, though.  Odd that such a nit picker would make a generalization about AT&T being the only phone company in the U.S.  If not for the mom & pop operations, many areas wouldn't have had phone service at all back in the olden days.  GTE wouldn't have existed if not for all of the mom & pops that it bought out to expand its network.

The 500 may have been a Kellogg, but the impressive phone was the 1500.  Getting your hands on one of those is no small task.  Or was it photoshopped?  Honestly, I don't recall 1500 or 2500 WECo sets having black-on-cream keys.  It was always white on grey, wasn't it?  Additionally, he could have found a 2500 with an older type of network to demonstrate the similarities to the 500 under the case.  Indeed, plenty of 500 bases were used for the 2500, keeping true to WECo's form of recycling and redeploying components.

I commented on the video.  He's dead wrong about the Dick Van Dyke ringer being a 500.  That's a chime box set to ring normally.  I can recognize the sound of those oversized gongs anywhere.

As for the various local exchange carriers across the nation, only the west side of Los Angeles, Santa Monica, and coastal communities to the south were served by GTE.  Downtown and the rest of greater L.A. was served by Ma Bell.  When I lived in Santa Monica in the late '70s, I hated my GTE-issued AE phone set and replaced it with a vintage Stomberg Carlson which had one of the most pleasant sounding ringers I've ever heard.  I wish I still had it.  Still, I prefer WECo products.  There's just something not right about having the fingerstop all the way down at the bottom of the dial. 

Verizon sold off their small service area locally to Frontier a couple of years ago, I think.  It resulted in many complaints due to failures in the internet access part of the operation.  A very sloppy transition. 

This little GTE/Verizon/Frontier pocket serves some of the more expensive neighborhoods in Silicon Valley.  When we moved out there in 1989 (to an affordable section nearby), GTE was still the provider and service sucked.  It improved significantly after GTE became Verizon.  We had landline service there for 18 years, and by the time we left, the Verizon switching equipment was superior to what SBC/AT&T was offering in much of their adjacent service area.

I remember long before divestiture, probably in the mid to late '70s, a friend of my aunt and uncle worked for AT&T.   Even back then, before I ever lived in GTE territory, I knew how inferior their service was and mentioned it to him.  He replied, "GTE is our best form of advertising."