Or what the Temple of Time is doing so far away from Castle Town.
I know this isn't the place to nerd out about Zelda lore, but I can't help myself, I apologize in advance. Lol
Anyways, it's just a new Temple of Time. Obviously, at least imo.
The Great Plateau is where the Sealed Temple once stood, and thus the birthplace of Hyrule, given its relative location to Lake Floria, Faron, and the Spring of Courage (Skyview Spring,) the temple we see in BOTW however is not the original one that was once built over the Sealed Temple, it's a new one that was still in use as recently as 100 years before OOT.
The timeline of the temple would then go:
Built over the Sealed Temple -> Moved north to sit inside Castle Town for protection -> Moved into the woods in TP to hide it from Ganondorf after OOT Link warns the Royal Family of his plan.
-> on whatever branch BOTW is on a new one is built in the same relative location as the original Sealed Grounds/Temple.
Also, I don't buy that the Great Plateau is Castle Town or that the Forgotten Temple is the Sealed Grounds. The similarities are tenuous at best imo.