This is a poor article. It makes no sense. It does not describe what white box testing really is.
It is different from the black box testing as the white box testing is not used to find missing functionality of a software
Like what the hell is that even meant to mean?
None of the advantages or disadvantages make any sense or related to whitebox testing at all. It is just words that are related to testing throwing around in hopes they mean something. Do not bother reading, it is not worth the effort to click on that link.