I'm pretty sure the pump in the PNSD0060DO2260 is a Pentair Dynamo pump (I remember looking at it a couple of years ago). I haven't looked up the GPM rating lately (don't remember right now which size Dynamo). But, as you say, the filters in the matched sets are always smaller than the recommendation in the Hydraulics 101 table. [edited to add: In this particular Pentair matched set, I think flow rate and filter are closer to being matched than in many other packaged systems out there.]
I believe there are significant flow differences between different pumps with the same apparent HP rating. Apparently there is no consistent meaning to the HP number (and there are terms thrown in such as 'up rated' and 'full rated' and 'service factor' which distort the HP numbers the manufacturers put on the units). If you take a look at the pump curve table [edited: I actually meant the "2 Speed Pump Flow Rates" table] for two-speed pumps (also near the top of the Hydraulics 101 thread - post #2 in the thread) you will see that flow rates vary quite a bit for supposedly the same HP.
I wish I could trust some of the cheaper dual speed pumps out there (like this Doheny one, for example), but information on them seems hard to come by. On a different issue, I don't think I would buy this particular pump, simply because of the digital control stuff built into it -- just one more thing to fail, on a pump from an unknown manufacturer, is how that looks to me.
and I would get the 1hp 2 speed
So, here's the Pump Curve for a 3/4HP Dynamo pump. (Not sure if it's exactly the same as a 2-speed on high, but I'm sure close enough for us amateurs) It appears, in actuality, that the 3/4 HP Pump can generate 70 GPM of flow with 10' of head. So the original 2-speed 1HP Doheney Pump that started the thread probably could generate 75 GPM of flow with an extremely low head, just like the Dynamo pump from Pentair in the graph. Depending on head loss it could be much lower. Maybe that's the reason the sand filters packaged with the 2-speed pumps seem smaller that the table in Hydraulics 101 mentions. On the graph above, can we assume the normal/actual GPM flow of these pumps is in the middle of the curve, maybe 35 or 40 GPM? Would that observation be on track? (Allowing for length of pvc plumbing/pvc elbows/ or other things that add head to a pump line) So when selecting a sand filter, you would not necessarily match this 3/4 HP Dynamo pump with a GPM of 70 and 10' head in the graph with a sand filter that has a GPM flow rate of 70 GPM to match it. Is that the reason the matched sets never have a filter as large as the table suggests? It appears, trusting the reputable manufacturers combinations may our best bet regardless of what the Hydraulics 101 table for filter sizing states, as we will never have enough motor/pump information at our finger tips to make the optimum selection for separate pieces and the manufacturers never seem to use the larger GPM filter the table suggests as optimal. We are most likely going to over size the pump and undersize the sand filter if we purchase each piece separately. I realize the matched sets are less expensive than buying a motor/pump/filter as individual pieces, but are the matched sets coming with an undersized sand filter?