These Freedom passes and the like came about after the introduction of condition 19 c (or those that I am aware of did anyway).
If a passenger from Redhill wishes to commute into London and then use public transport around London, they can obtain an outboundary Travelcard.
If a passenger from Stalybridge wishes to do similar, but commuting into West Yorkshire, there is no equivalent of an outboundary Travelcard, so they would obtain a Stalybridge - Marsden season and a Metrocard (other combinations involving a longer season and a Metrocard with less zones may be more efficient - this isn't relevant to the point). If, for the purposes of Condition 19 (c) both were treated as seasons, then they would be restricted to the hourly stopper which calls at Marsden. As the PTE product is not treated as a season, they are able to use the quicker and more frequent express trains, equivalent to the Redhill punter with their outboundary Travelcard.