Comment by AnonC

So basically, Mullvad is saying that you can use its VPN aeevice as a client to reach services but not host a service yourself (especially in a home network behind NAT or CGNAT) and have others connect to it via the VPN.

The most commonly used scenario for port forwarding would be torrenting, where users forward ports so that they can be “connectable” (i.e., accept incoming connections from the Internet).