I noticed that Amtrak's "line up and wait for no purpose" boarding applies at Grand Central.
The platform (Track 38) is accessible from the north and the south.
The Amtrak train is the only train the entire station that is not Metro-North, and the only one in the entire station that has a color scheme and shape unlike Metro-North trains.
There was an Amtrak crew member near the south entrance to Track 38, directing people where to go.
The train had been serviced and looked ready.
So couldn't Amtrak just let people do as they normally do in Grand Central: just walk up and board?
Of course not. Passengers had to line up at the south end of Track 38 and wait before being allowed to board--even though to do so, for people coming from north of the station, required walking all the way to the south end of the platform just to stand there and wait.
Ridiculous.