Train Simulator 2016 (2017 Base + 2016 Routes)

Either way, so long as what SG is listing is the app for Train Simulator (base game) and not the subs (that actually compose the yearly releases), I suppose it's technically correct to list any edition of the game under the giveaway, since they all do give the necessary app (regardless of what the page that houses that app is currently titled). :X

I presume that people that own one version of the game can't enter giveaways for new versions of it either, since ownership of the base game would prohibit that. So in that sense, treating them all as the same app works suitably.
So perhaps your approach of simply making it very clear which routes are included is best (if SG doesn't put up the individual subs)..?

For an example of what STB is talking about, here're the apps for the 2016 sub, which includes the Base 2017 game and the 2016 core DLCs: https://steamdb.info/sub/78707/apps/

Here is what we actually got with the recent Humble bundle, which differs slightly:

https://steamdb.info/sub/75320/apps/