I have used the book to help me parent my daughter, and have to say that, while we don't tie her door shut we *do* have a portable stair-gate across her door at night so that if she wakes up she doesn't come into our room but stays in her bed and shouts us to her. This is because she doesn't lie still in our bed - she kicks and wriggles and no-one would get any sleep if she were in with us.
The section you refer to does sound old-fashioned now, but it is one part of one chapter, and all it offers is a suggestion for stopping a determined toddler from getting into the parents bed or having the run of the house. The whole idea is that the door can still be opened, but only a few inches. It's a last resort for parents who are desparate for a night's sleep. If you don't agree with it no-one is making you carry it out.