It does look short, but looking at OE models from model train manufacturers (Marklin, specifically) it's correct for the loco (without the tender) to be about half the length of the passenger cars. That said, the passenger cars are shorter than prototypical, likely because they have to work on R40 track, thus the loco gets squished too.
I may get two, to extend the passenger cars a bit and still wind up with an extra one and also make adjustments to the loco!
Conveniently the OE has been around for a LONG time in different reincarnations, so just about any locomotive could be "correct" on the front of it, even modern stuff that was operating in 2022 when I photographed it:
https://flic.kr/p/2ntzTiW