I don't think reading any number of pages can give you expertise in programming. Doing is where you get the expertise and since you don't get expertise from doing only doing backups and restores you can't put a time frame on how long you need to work with SQL to be considered a specialist. That is touched on in the editorial but I don't think it was stressed enough.

Generalists still have a very important place in being able to put all the pieces together. I've worked with some developers that could put their hand to pretty much anything. They were key to the company because they could take a big view of the application and weigh in on both DB and compiled code. They also had years and years of experience so it was something that they had gained over time. It certainly takes longer to become a good generalist but the people that do it deserve a lot of respect.