The post by Matt Birchler has been amended with the paragraph "A previous version of this post suggested the DPAN changes between merchants, but that was a mistake. Serves me right for cranking this post out too quickly. Seriously, my bad.". However, the rest of the post still suggests that there is a unique DPAN per merchant, but I can't find any basis for that.
Even Apple's own documentation at https://support.apple.com/en-us/HT203027 says that the DPAN (called Device Account Number here) is only unique per device. When a card is added to Apple Pay a DPAN is created for that device, and it never gets changed afterwards unless the card is removed and re-added.
So whereas you can't be tracked by using the same card on two devices (e.g. iPhone and Apple Watch) because they will have two different DPANs, I'm pretty sure data brokers can track you when using the same card on the same device across different merchants.
Even Apple's own documentation at https://support.apple.com/en-us/HT203027 says that the DPAN (called Device Account Number here) is only unique per device. When a card is added to Apple Pay a DPAN is created for that device, and it never gets changed afterwards unless the card is removed and re-added.
So whereas you can't be tracked by using the same card on two devices (e.g. iPhone and Apple Watch) because they will have two different DPANs, I'm pretty sure data brokers can track you when using the same card on the same device across different merchants.