Hi there @bacondude
I'm Dez, a Community Educator here at giffgaff. I'm just making contact about your concerns.
I can confirm that the website you mentioned is blocked. i've just tried it on my sons phone (17) and it is not possible to connect.
Would it be possible for you to screenshot a small section of your settings page on the affected account and post it here. Please don't post any personal information - https://www.giffgaff.com/profile/details#adultcontent
Now press close.
This is what my account shows but I have entered documents to remove the content lock. Your account must show off.
If the setting is as you say allowing connection then do contact an agent to look into this further