Exactly my underlying concern here! What is best for the plant - since the main function of downward motion seems to be to accommodate the new rings of roots that grow above the old ones as the plant goes through blooming seasons. And, especially if there is some kind of increased stress that may increase their borrowing, perhaps due to extended 2-3 month extreme heat (100+). The article does give very good evidence that downward movement occurs, but also notes other plants that are more able to keep repositioning as needed (up and down). It seemed like daylilies, having burrowed down, may be unable to "right" themselves and get back up when critical conditions have passed ...
I know I will be thinking about this long and hard in the next few days before I start a final push to get fans set for the winter. If they need to stay near ground level, even under extreme conditions, I'm wondering about some sort of stabilizing structure, something like a fixed horizontal rod or even a large-gauge screen the roots could grow down through, but that the crown could rest on, fixed at a height so that repositioning crowns so often would be less necessary? With so many fans to attend to, and the longer between-times of tending to them during winter... I might just try this out ...