Might be that we have more precise door builders than other parts of the world but from a German perspective that gap is huge and I don’t think I have ever seen one that tall on regular internal doors (as opposed to e.g. outdoor shed doors or similar places where insulation is taken less seriously).
The cat has access to all the rooms. They can, and will, crawl under the doors of most houses.
What kind of tolerances do your doors have that cats can crawl under them?
¼" to ½" is all most cats need. They are surprisingly flexible
Since cat skulls are 1.5-2" in the smallest dimension, big X to doubt on this one. Unless your cat can deform it’s skull like a squeaky toy
https://www.youtube.com/shorts/qFzdp4iaQhs
definitely more than 1/4"
Might be that we have more precise door builders than other parts of the world but from a German perspective that gap is huge and I don’t think I have ever seen one that tall on regular internal doors (as opposed to e.g. outdoor shed doors or similar places where insulation is taken less seriously).