I diagree with 'interchangeability". they are not the same. for example Rahr 2 row is about 1.8L-2.0L whereas their Pale Ale malt is 3-3.5L
the Rahr Pale Ale malt has a candy-like sweetness that I do not care for, and as such I always avoid the Pale Ale malt, opting for 2-row.
as was said, I believe that "pale ale malt" is typically a maltster's take on making some approximation of maris otter malt. but when I want maris otter, I just buy maris otter, much better IME.