So nothing should change even if it makes zero sense?
Not if it isn't causing any practical problems to anyone, and nobody has yet produced any evidence that it is. it may be a slight misnomer, but so what? Nobody is turning up there expecting to catch an international train and being surprised when they can't, are they? It's a non-problem.
Stratford Westfield would be rather pointless, as far more people arrive at Westfield from Stratford station than from Stratford International.
Perhaps, but I'd also suggest that the majority of people - probably a significant majority - using the station are doing so to visit Westfield, so it makes sense from that perspective.