Some IP addresses are more personal than others.
What I mean is that yes, on it's own an IP address does not pinpoint persons, but devices. So it remains upon the complainer in the case of a copyright infringement case to present a further reasoning 'above the speculative level' that the by the IP identified device at the time of the infringement was under the control of the alleged infringer.
In this case they failed. That doesn't mean it will always fail.
If you're mobile ISP uses IPv6 for everything and assigned your mobile a static IPv6 address, then it will be harder to argue it wasn't you.
If you're Home router is provided and managed by your ISP, and it is configured to use DHCP Static Leases, then the local IP of your mobile phone (a fairly personal device) is close (not equal) to being equally as effective as a personal identifier as it's MAC.
If on the other hand you connected to an Open-Wifi set up by an amateur 4 NAT's down that does not keep logs, and you randomize your MAC every time you connect to a new network, it might be more difficult for tying an IP to your device without reasonable doubt.
In that last case if the pursuer wanted the open-wifi operator's operation could be made more difficult by DMCA complaints and leverage through the ISP's terms of service.
In this case they failed. That doesn't mean it will always fail.
If you're mobile ISP uses IPv6 for everything and assigned your mobile a static IPv6 address, then it will be harder to argue it wasn't you.
If you're Home router is provided and managed by your ISP, and it is configured to use DHCP Static Leases, then the local IP of your mobile phone (a fairly personal device) is close (not equal) to being equally as effective as a personal identifier as it's MAC.
If on the other hand you connected to an Open-Wifi set up by an amateur 4 NAT's down that does not keep logs, and you randomize your MAC every time you connect to a new network, it might be more difficult for tying an IP to your device without reasonable doubt.
In that last case if the pursuer wanted the open-wifi operator's operation could be made more difficult by DMCA complaints and leverage through the ISP's terms of service.