Here's the context.
John saw a girl dancing in a bar 3 days ago.
Jihoon saw a girl studying in the library yesterday.
The two girls are the same girl.
In this situation,
The girl John saw dancing in a bar 3 days ago is the same person as/that Jihoon saw studying in the library yesterday.
Jihoon saw the same girl studying in the library as/that John saw dancing in a bar.
John saw a girl dancing in a bar 3 days ago and the girl is the same person that Jihoon saw studying in the library yesterday.
I've made 3 sentences to understand how to use 'the same~' sentence structure. And I think these are all possible to use and the same meaning. Or is there any difference in meaning? And I think as/that are all possible here, but I do agree that there are some people who stick to using only one of them