If you had a book which had on its Contents page:
Chapter 1 . . . . . . . . . . page 1
and you crossed it out, then wrote:
Chapter 1 . . . . . . . . . . page 1
Chapter 2 . . . . . . . . . . page 50
someone looking for Chapter 1 is still going to find all the text in the right place (as long as it was less than 50 pages).
Changing the partitition table is like changing the Contents page; it doesn't mess with the rest of the data. And if the new table points to the same place it did before, the data can still be found.
That said, if the filesystem still thinks it's 1TB, you may end up with future problems unless you resize it to fit the reduced partition.
Ah, Enhanced, the folks that brought us interrogation.