A similarity between the Fosters' home and the Tucks' home is that both are isolated from the rest of society in one sense or another. The Tucks' home is literally isolated because it is located in a very remote place, whereas the Fosters' home is isolated simply because it looks uninviting.
When Mae Tuck decides she has no choice but to bring Winnie home with them so that Tuck can convince her to keep the secret of the spring, Winnie travels with the Tucks for a very long time. Towards the end of the journey, she climbs a "long hill" with them followed by a second long hill. Beyond the second hill, she sees the "deep green of a scattered pine forest." It's within this pine forest that the Tucks' cottage resides. They must live in a remote home, far away as possible from other people, because people begin to grow suspicious when they see the Tucks are not aging. The Tucks know that people's suspicion can lead them to discover the Tucks' secret, which is very dangerous for all of humanity.
Similarly, the Fosters' cottage is situated near a wood that the Fosters own. People of the village never enter this wood, partly because it belongs to the Fosters and mostly because the Fosters' cottage has such a "touch-me-not" appearance to it that strangers stay away from the wood, the cottage, and the Fosters in general. In describing the Fosters' cottage as being a "touch-me-not cottage," the narrator is saying that the cottage looks so pristine and perfect that it looks cold, distant, and intimidating; therefore, strangers stay away from the cottage, just as people stay away from the Tucks' home because it is so remote.