Question on GSB removal

[lkc0626]

Hi, I may be asking it wrong place but this is the best place to ask about this since this library has been developed based on GSB API.
I'm trying to analyze GSB and its behavior. However, I don't understand why and what URLs GSB removed and many of them are reappearing. Also, there are almost 80% of them remain in the GSB when I do a full update.
This library is developed based on GSB API and this helped me understand GSB a lot better so I wish anyone here could help me answer my question would be thankful.