This is typical glove-hawker advice. The passage redtail's mainstay is hunting from poles and they have an advantage from the height. Pole hawkers take this as a blessing, but glove-hawkers believe that allowing them to continue this habit reminds them that they got along just fine without you. One day, they might decide they'll just stay up there for the afternoon. Correspondent to LG8, if you train your bird to hunt from the glove, you can train them to pole-hawk later, but it's harder to go from poles to glove.