O1 is an alloy. The term "spring" isn't an alloy, but a reference to hardness. It doesn't make a lot of sense with O1 because spring steels are generally water hardening types (there's no reason to spend more for an alloy that hardens easier if the thing being made is really thin like a saw, and softer like a saw (water hardening steels are usually low toughness, but at lower temper, everything is tough, it's just not strong. Strong means stiff more or less, tough means won't break as easily even if it's allowed to bend).
Short answer, you don't know what the rider blade is and the retailer probably doesn't either. A stroke test would clear things up quickly as water hardening steels at the same hardness will only plane about 75-80% as long as O1 (except for 52100, and it won't be that).
You can ignore jacob's comment if you use a powered tool to grind the iron - O1 grinds easily. Hock's irons are good irons, but not sure what they go for there (they're about $40 here including shipping for a 2 inch plane iron, which is a fair bit more than they were a couple of years ago).
The average beginner will find them easier to sharpen because they're hard and they don't hold a wire edge that easily (And if you use the same sharpening process with them vs. a stock plane iron in most planes, you'll be able to take a thinner shaving).
Axminster also claims 63 hardness on their irons. You'd love to see someone test five of them at random and see if they're actually at as most makers chasing high hardness will just give you something chippy. Not sure where the "rider" planes are made, but O1 doesn't come too commonly out of india or china, and though it's a pretty easy steel to deal with if it comes rolled and prepped well from a mill, if you don't follow the rules, you can make anything poorly.
