Some applications use those unused bits to add tags to pointers but it’s important to mask those out before attempting to dereference the address. I’m not sure about ARM but x86-64 requires bits 49-63 to be copies of bit 48 (kinda like sign-extension), ironically to ensure that no one is using those bits to store extra data.
I wonder if the intent was to actually send users to these sites, or to generate bogus clicks on ad links.
Seems like a lot of effort to go through just to drive a little extra traffic to some random porn sites.