Forgive my assumptions and limited knowledge - and I'm trying to word this in a respectful and polite manner, and I know nothing I write will be new information to people here - but from what I've read on here and elsewhere online, I'm sort of under the impression that AFOLs (or at least the train focused ones) who wanted the Orient Express, didn't actually want the the Orient Express - they wanted a highly detailed model of a locomotive, any locomotive, to the extent the Orient Express hardly even appears on the cover of the Mould Kings Orient Express set.
From what I understand of the history of the Orient Express, it is only the coaches - it's even the company name: "Compagnie Internationale des Wagon-Lits", the locomotive power was simply contracted out to the various state railways. It would make sense therefore that any set depicting it would therefore focus on the sleeping and dining cars - to omit either one in favour of a bigger locomotive, which I've seen people suggest, would miss the entire point of the Orient Express. Then, if the coaches must be the centrepiece, sacrifices had to be made elsewhere.
Supposedly, the IP holder (which I believe currently is 50% SNCF and 50% Accor Hotels, who are planning to officially relaunch the service in 2025) had a much greater input than normal compared to other IP holders, and, according to one video I have seen from someone who attended the Lego Press event, chose the specific engine they wanted it to be based off, and what colour it should be (the video never said which locomotive it was only that the Lego designers didn't have access to it as it was off doing Orient Express things and we're provided with schematics and images instead - which I'm guessing is pointing towards the locomotive pointed out by @LEGOTrainBuilderSG. Why they decided on this is anyone's guess, but aside from economics at Lego and real world exhibitions, I also imagine it was a question of balance. In the original submission and the Mould Kings set, the locomotive is the centrepiece, it dominates over coaches, and much more attention and detail is put into it than the more boxy looking coaches - it arguably detracts from the Orient Express by pulling focus away from it instead of complementing it. You can easily see why an IP holder would want something with their brand be the focus of it rather than the accessory.
I have to be a bit cynical here, but I'm doubtful this set would have made it without the Orient Express name - looking at the Ideas website, the Mallard and Flying Scotsman seemingly have plateaued at around 5k votes with time quickly running out, and they are famous named locomotives the general public are most likely to have heard of. The only other train sets that seem to have a better chance are those with an attached IP, such as the Polar Express. So a random unnamed French railway locomotive would have no chance.
Apologies for rambling on, it's late. Especially as the conversation has moved on from the locomotive to the locomotion.
