I haven't seen that arrangement in a while.This sounds like an upgraded or refurbished arrangement to me.
My impression was that each block of 5 roomettes was on its own circuit, and I have had the circuit go out in my room while I wasn't doing anything but charging a phone. If that happened in the middle of the night, the power stayed off until the attendant discovered at 6 in the morning that the coffee pot in the hall wouldn't start.
I think the people who have gotten lucky with high-draw appliances have just happened to not have anyone nearby doing the same.
But I only was there to see the attendant open the panel once, several years ago now, and I didn't take a photo.
Inclusion of an AC outlet in trains, planes, and yes, even buses began wayyyy before modern electronics, and was originally to accommodate them there newfangled electric razors. They stumbled along for years until hair dryers, curlers and he rest of the current crop of devices came into the mainstream. It became much more efficient to install a power bus with individual branches. Customer complaints were reduced, safety was enhanced. GFI devices made it even more so. I haven't seen a 2 prong outlet in a Supeliner in a long long time.
For a long time the NEC exempted wiring in vehicles, but many local jurisdictions enacted codes superseding the NEC. When designing TV remote units, I had to factor in all the local codes plus the even more stringent Canadian codes.
As I am indeed among other things an Electrical Engineer, I have prowled AMTRAK equipment equipped with flashlights, lock opening apparatus and an inborn desire to know how things work.
It has been a very long time since I have seen an original design Superliner, which indeed have a block electrical system as you describe.
This knowledge has come in handy, I have shown several SCAs how to fix balky HVACs, even a sleeper toilet system which threatened to Bad Order an entire car once on the Crescent.
The upgrade path to LV lighting controls, solid state PA and music systems, even the video players and displays in the rooms (now long gone) has been a rocky path. The constant mechanical stress on things have shown that you can't just toss a couple of VCRs in a cabinet and expect them to work for very long.
Those coffee urns upstairs in the Superliners are heavy current items, and the elements are prone to fail, tripping a branch circuit.