As a fairly new DIYer, I can sympathize with Sephora - I'm in the middle of a bathroom reno right now, but shortly will be moving onto kitchen stuff (backplash and new cabinets...why I'm starting to peruse these topics). I've been told varying things by varying "people" - some pros, some not, and some "helpers" at HD, and books and websites. It gets confusing. Everyone has their own way of doing it... you even see that on the copied directions above.
In my limited experience, I've adopted a personal rule so far: go with the most "conservative" approach that is reasonable. It may cost a little more (usually not too much on smaller projects). It may take and extra few steps (read more time). But, in my obsessive mind, I'll be more at ease, not wondering if the drywall is rotting behind the nice facade, not thinking about water vapor or damange, or worse.. an inspection at a later sale date. Just my 2 cents.