First off, Uwu, trains are nowhere near like the tech in botw.
OK, I'mma spitball here, but, I think that BotW may not actually be in any timeline that we know of, so far. I think this because BotW fits all of the timelines... except doesn't. Possibly BotW is an alternate timeline and could...
So the only good evidence for Child Timeline is geography that is similar to TP? I wouldn't take that into consideration - it's more of a design choice.