They can't see the VPN logs but there are enough fingerprints placed in things like Cookies, unique hardware ID, DNS.For me, I use a VPN to spoof my country to get around YouTube blocks. However, what is the point of a VPN if you're trying to hide something and the ISP can see the VPN logs?
Not familiar with Pr0nhub, but I think as long as it's legal, then you don't need a VPN? I think ISPs / police will be more interested in people who use illegal pr0n, torrent sites, terrorist plots etc.
All VPNs do is kindly aggregate all of your activity together and put it in the hands of an unregulated private company who make wonderful claims