What is "Archaeological Evidence" when Collected by Collectors?

Leicester FLO Wendy Scott approvingly tweeted a slide from a presentation by Jane Kershaw talking via Skype about "the value of PAS data" at the pro-looting 'chance or challenge' conference in Aarhus. This is dot-distribution maps gone absolutely bonkers.

Can you see that? The researcher is plotting out coin finds of 650-750 and equating lines of them with roads - including new ones, and a lack of finds is supposed to be showing where roads "went out of use". I can't help comparing that map with the PAS "affordances" maps and wondering how one can apply archaeological interpretations when what clearly is being mapped are modern collecting practices. I also ask what the connection is supposed to be between movement on a road of a specific type (as opposed to waterways) and the usage and deposition of coins and how those assumptions were tested. Do Elizabethan coin findspots, for example also "show which Roman roads were in use" in the sixteenth and seventeenth centuries (known from the early county maps). Were roads the only way coins got into the ground?

What, actually is "the value of PAS data" and what kind of data are they?