They're only from Newquay to Pad, not Pad TO Newquay.
I think that they'll find to their cost that a Sprinter that connects off of the 1st one down to Penzance simply won't cut the mustard, because I've done the Pad to Newquay run as a day trip twice and that was rammed all of the way and that was a full HST 9 set, every seat was taken + full & standing.
I think that GWR have made a horrible mistake taking that first one down away from Newquay & sending it to Penzance instead on a summer Saturday. It would be better if they used the Sprinter from Par to go to Penzance & back to connect into the HST from Newquay. Still it's their train set, let them find out the hard way.
I've got some reliable inside info on this one.
I think you will find that things have changed quite noticeably over the past 2 years. Quoting a 2+9 formation dates your trip to at least 3 years ago, pretty sure that's the last time the HSTs conveyed the extra TGS on Newquay diagrams. Since then, summer SO traffic by train to Newquay has literally fallen off a cliff edge, thanks mainly to ticket prices being undercut by a certain budget airline operating from (I believe) Southend. The passenger counts from 2016 indicated loading not exceeding 200 even on the 1135 Padd-Newquay on the branch, and one train in particular arriving at the resort with about 35 pax. These are data from August summer holiday dates.
At the same time, Cornish main line traffic goes from strength to strength and some trains are creaking at the seams. As the 0735 Padd-Newquay and 1319 Newquay-Padd were added to the timetable within the last 10 years to relieve the ACE, it seems logical that GWR would choose to divert the resources where it is needed most. Last year the 0928 Exeter-Penzance Sprinter was leaving passengers behind at most stations after Plymouth hence why it has been swapped with the Newquay path.
(Also note; the 0946 Exeter-Newquay and 1323 Newquay-Plymouth will connect with the HSTs at Par and are diagrammed a 4-car sprinter, capacity 300+ so it shouldn't be overcooked on the branch.)