The stability of the PTS price suggests that there's market consensus that PTS is different; when Bitcoin crashes it brings all the other bitcoin replicas with it, but PTS is in a different asset class so it weathers the storm.
The other thing to remember is that the value of PTS specifically comes from controlling the private key, so I bet that most PTS is held in private wallets instead of in online exchanges. Since there's less of it out there available to sell at the drop of a hat, its price movements are more muted.