I recently bought a "large tall" size shirt from Drysdale's. When it arrived, although the tag did indeed say "large tall", it was certainly somehow mislabeled because it was much larger than any "large tall" should be. My guess is that the shirt is the size of a 3XLT or 4XLT. Because it is my size, I own a lot of "large tall" shirts, and one of them is shown in this picture for comparison.
Although it is true that exact sizes may vary between brands, clearly this shirt is quite a ways outside the range of shirt size which can reasonably be called "large tall". Furthermore, at the same time I purchased a "large tall" hoodie sweatshirt which fits great and is exactly in line with the rest of my clothing.
Drysdale's service department was very helpful and courteous. It was a sale item, probably the last of the stock, which they did not want returned, and they refunded the small amount of money I had paid for it. Thank you, Drysdale's.