TSW 5 introduced new achievements for all the new routes base game and all added routes/locos/gameplay packs near enough with the odd exception of some older TSW Routes. Cajon Pass comes to mind which im sure was a base game release for TSW 3? Odd choice in my mind given the age of the route. Additionally, Some achievements I've earned on much older routes that are present in "newer" versions, such as East Coast Way for TSW 2020 havent popped on TSW 3, indicating potential bugs as is. Preferably I would see it best they only release achievments for that version of the game from now on. I.E TSW 6 will have its own new routes base game then of course DLC. By all means keep what content they can compatible, just if you want to earn achievements for older routes, play them on the version of TSW they are originally from, or a TSW that supports their achiements
