The second statement: children usually bring umbrellas at home, so some people think that bringing umbrellas at home is not conducive to children's growth.
The third way of saying it: the homophonic word "scattered" means "scattered wealth, scattered home" indoors, so the umbrella is used outside, not at home.
The fourth statement: Britain has a similar ancient legend. If you open an umbrella indoors, something very unfortunate will happen. It will be a disaster. Moreover, if you see someone holding an umbrella indoors in Britain, the person who sees it will feel very uncomfortable and will make you put it away.