An unintended consequence of using the TSW game template I suppose, but I don't find it to be an "issue" more "feedback." As in... I like it as it is. Don't fix anything. TSW trains aren't natively IN Sodor, so if you don't want them... you don't have them. However, if someone wants them in, you can just copy them into the other game locomotive folders and viola! But, you have to go out of your way to do it, so it's a conscious choice to do so. It's the best of both worlds. Please keep this as is.
It would be great if console players (I am on PS5 myself) were able to port TSW stock over to WoS (and vice versa), like when you upgrade from TSW5 to TSW6.