Clarification
 

I'm assuming that "Kettles" is slang for an overweight American packs too much garbage into their oversized wheely-bag. They are obviously people who fly only 1x or 2x a year.

The only flights they seem to even physically able fit into are on 777 and a 747.

Yes. About 12 years ago on a United flight (ORD-SAN I think). It was during Thanksgiving or Christmas, and the GA gave a good reason for skipping the elite boarding. The flight was completely full with about 80% being elites
(my memory may have failed me a bit here about the exact fraction of elites, because this was a long time, but I recall it being an impressively large fraction).

I was on a ewr-bos monday morning flight where I was probably the only non-elite on a full flight. Clearly elite boarding would not have been very helpful in that situation.

In another situation, I recently took a flight EWR-PBI where they starting boarding ~40 minutes ahead of departure. They didn't call rows or anything, just whenever you showed up you got to walk on board.

The (IMHO manufactured) drama is the difference between the elite boarding processes at UA and CO. UA only lets certain tier levels board using the red carpet and then puts the tensabarrier across barring access. CO lets all status fliers walk across the blue carpet.

Personally, I can see both sides: yeah, I find UA's decision petty and generally unnecessary; but the UA gate agents are a lot more effective at enforcing the line, even though it often reminds me of Ferris Buhler's day off: "Global Services?" "Global Services?" "You're a Star Gold? Please wait against the wall." "Global Services?" "Global Services?"

Too Young To Know
 

There was an old radio show called "Ma & Pa Kettle Back On The Farm"

(but your description works)

AND there were some Ma & Pa Kettle movies!

I literally had this happen to me in SFO. I was on a redeye flight and I wanted to get on the plane and go to sleep. All of F and 1K/GS had boarded already (I think everyone had been upgraded). I knew *G came after so I proceeded to walk down the red carpet, since no one else was around. Well, the GA was not happy with a peon stepping on the sacred red carpet. He started interrogating and I explained I was a CO plat and that no one else was around to board. He snapped at me and proceeded to open the barrier to the regular line and have me stand there and put the line in front of me. I felt like Greg on Meet the Parents. About three minutes went by and no VIPs came and the GA finally called *Gs and 1P and 2Ps. When he did, he of course closed off the red carpet for business. I guess he delayed the boarding process to teach me a lesson? I have other controlling carpet stories, but I will stick to one to keep this post short.