I'd bet it's because the filtering vendor (Allot) sells a simple interface to the customer (Vodafone) that mostly consists of allowlist/blocklist entries manually added by support agents when someone complains.
There's probably a policy to dictate what content should be filtered, but in practice: a ticket is filed to block a site, someone looks at the ticket, in all likelihood it is added to the blocklist, and then probably ends up there forever until complaints are raised.
You could be correct that the presence of multiple x's in the URL makes it more likely for support agents to think "yep, this is probably sketchy, there's no harm adding it to the blocklist" - I doubt it's the original reason though.
