The main distinction in my mind is that every node in a p2p file system is essentially the same, whereas nodes in a non-p2p distributed file system are not equal and are often specialized. For example, LizardFS is a distributed file system but has master/shadow servers, chunkservers, and metaloggers (not sure if you'd count clients as a separate node type, but I would).
Distributed file system
Distributed filesystems generally allow the function of each piece of their infrastructure to be split across multiple machines for performance, scalability, or fault tolerance. What that looks like in practice depends on the specific file system implementation (e.g., Ceph, GlusterFS, LizardFS, MooseFS, etc).
Reference and more information here.
distributed systems in which all nodes have identical capabilities and responsibilities, and all communication is symmetric.
P2P systems would be a subset of distributed systems.
Definition copy/pasted from here.