You're absolutely right, though to be fair "whilst" is a more archaic form of the word. They have to manually put in all the accepted responses to fair enough that they couldn't cover all synonyms. Good call mentioning it though
It means a general fact, but it can be a general fact about a particular group of cat and dogs (say, those in my house) - so this may be true. And then the given Hebrew sentence would be the normal way to say it, so it should be accepted.
If you use “when”, the meaning changes to “In the event that the dogs stand, that’s when the cat sits”. “While” means two things: “the cat sits but the dogs stand” or “the cat sits during the time that the dogs stand”.