@goedric @seedfork
There is no problem related to dormancy with growing daylilies inside during the winter, I have been doing so for many years without problems.
There is no objective evidence that any daylily needs to experience a period of near freezing cold for good growth and there is objective evidence that all or nearly all daylilies do not require any near freezing cold for flowering.
If you leave your daylilies outside so that they experience winter cold then some of them may go dormant. When you bring them inside and give them good growing conditions many of the dormant daylilies will start into growth quickly with no problems. It is possible that a few of the dormant daylilies may stall (start growing and then stop). To get those to grow may require patience but I have found that giving any that stall warmer temperatures and high light (closer to outside light intensities and temperatures on warm spring days) gets them started into growth in less than a week.
It is simpler, in many cases, to simply bring the daylilies inside before they show signs of slowing growth (before they lose their new leaves). I am in zone 4 and if I bring daylilies inside by Oct 15 they grow without problems. Stout was in New York city and he found that daylilies brought inside into a greenhouse without extra lighting about the middle of November grew well.
All daylilies may experience a period of dormancy, whether they are growing outside or inside. That may partially depend on how well they are grown and the temperatures and watering that they receive. It will be affected by how well they are fertilized. Dormancy is a period of time when a plant stops growing. That can be seen by checking whether a daylily is producing new baby leaves in the centre of the fan on its normal schedule (which depends on temperature, light, nitrogen fertilizer, etc.). It is dormant when it stops producing new leaves. It can be dormant yet have a full fan of green leaves. That is a normal response. It will start into growth again when its crop of leaves ages, yellows and dies. That is also normal, leaves have a limited length of life and then they need to be replaced. That is called discontinuous growth. If it is given optimum growing conditions it may simply grow continuously meaning it will continuously produce new baby leaves and slowly but continuously some of the older leaves will yellow and die.
How a daylily may react specifically will depend on your location, the weather the daylilies experience outside, the conditions they experience inside, when they are brought inside and what is done to them when they are brought inside (for example, removing all their leaves when brought inside or leaving them), etc.
