I don't have the books anymore so I am not 100% sure but I wonder if it was to avoid turning it into a habitual/snacking thing? Tbh though the things that are now know about bf mean the books are out of date in that regard and frankly if it works for you and your lo then by all means carry on until it becomes an issue. Sounds like it is working to get you both a nice stretch of sleep! We did not df with DD3, she would not rouse at any time I tried, and it worked out fine just feeding when she woke.