It was my intention that the refitted Endeavour is the first of multiple Columbia-class ships (or maybe the second -- I'm open to the idea that Enterprise was refitted to Drexler specs sometime during the Romulan War, since the books never say it wasn't). Since they're variants on the same class, it's possible people in later centuries could confuse the NX and Columbia classes.
But you do mean that during A Choice of Futures
/Tower of Babel
there are no NX class ships active, correct?