Miyuki couldn't care less about the sewing room door opening. She can't be arsed to wander upstairs to inspect.
Mercury is nominally interested in the sewing room. If I've been in there "too long" he will wander in and meow until I stop and reassure him with some petting.
Ziyi, on the other hand, finds something both fascinating and unsettling about that door opening and me being in "that strange room that only appears sometimes." She needs to keep a close eye on me when I'm in there and frequently demand attention, scolding me till I stop what I am doing and pet her.
And then there is Sam. Sam also needs a lot of reassurance when I am in the sewing room. Only he launches himself into my arms from the ground, which can be rather awkward when my hands are full of fabric. Sam also loves