Semi-opaque stain from semi-transparent base?

We just sanded and prepped our 8 year old PTP deck (20 x 14). We went to a local paint store and the owner convinced us Pittsburgh Paint Sun-Proof was a great stain (we went there for sikkens). We chose a semi-opaque. The base he used was semi-transparent and when we questioned it, he said that the difference between the semi-transparent and semi-opaque in this line of stain is in the tint and not the base. Is this true? I see on the manufacturer's website that they have different bases for ST and SO, so I'm feeling like we've been hoodwinked. Also, the stain is very blotchy, seems like little to no coverage in some areas, a silvery gray in other areas. Probably more like a ST and not a SO. We are not happy with the appearance at all. From what I've read, applying a second coat or a SO over it is not recommended, correct? So stripping and starting over is the best solution.

Please provide any advice on what we should do next and also on high quality SO deck stains as I am reluctant to purchase the Sun Proof line again. I definitely don't plan to go back to the local paint store unless I learn that he gave me sound advice regarding the ST being the correct base for SO. Deck faces south and west, very little mold/mildew, about 1.5 feet off the ground sloping to 5 feet, southwest michigan. Btw, we are re-siding our house once we figure the deck situation out so the unsanded wood you see in the photo (on the right) will be covered once this is done.