@Hemlady,
Your rule of thumb is as good as any other. Each grower can only classify daylilies as they see them grow in their own location and under their own growing conditions. They cannot know whether the growth pattern their daylilies show will be consistent in all locations or whether it will vary in different locations.
Here is a specific example. The ditchlily 'Europa' loses its leaves and has an underground bud here, and for Stout in New York and for Watkins in Gainesville, Florida where it had a long rest. Stout took Europa inside in November in New York and within a few days it started to grow and later flowered and continued to grow. It does the same thing when I bring it inside here in the autumn. So it loses its leaves makes a bud and stays underground because of the cold outside. As soon as it is warm enough, it grows. Even the mild cold of Gainesville is enough to send it scurrying underground and forming a bud. But give it between 60F and 72F, even with the short days of a New York winter and the low light intensity of a northern winter and it happily grows. So, in a greenhouse, where it experiences a winter that is warmer than Gainesville but not hot it does not stop growing. It would be registered as "dormant" here, in New York and all the way south to Gainesville, but it would be registered as evergreen anywhere that the winter temperature stayed between 60F-72F. It is an ecodormant. It stops growing, loses its leaves, sets a bud and stays under ground for a long rest only because it is cold enough (even in Gainesville). Where it is not cold enough it is an evergreen. Even after it has set a bud, etc. because of the cold, all we need to do to get it to grow again is to make it warm.
The registration categories and the actual growth patterns of daylilies cannot be relied upon to be consistent. It is not like registering a plant as having a yellow flower and knowing that no matter where or how that plant is grown it will have a yellow flower and it will never have a red flower. You can register a daylily as a "dormant" because it acts that way how and where you grow it but there may be other locations where it acts completely normally and just like an "evergreen". Biologically it is neither - it simply reacts to its growing conditions or environment and responds as well as it can.
There may be some daylilies that rather than ecodormant are endodormants. I will keep looking.
