The PQs aren't strictly soloable. Meaning that you can't complete them solo. What they meant is that even during the advanced stages of the PQ there will always be non-champion mobs that drop tokens and that solo players can kill (in addition to the group content, not replacing it). In usual PQs if you proceed to the advanced part of the PQ and you're solo you won't have anything to kill, because there'll be a bunch of champion mobs that will kill you, and nothing else.