um hum, I wonder who wrote this for Loft Home? Some indiscretions here to say the least. For one you either have mortise and tenon joinery or doweled joinery, not both in the same joint. So I think you can throw out the hard maple frames with mortise and tenon joinery as not being current, as this doesnt belong to any NC manufacture of fully upholstered sections. Maybe some imported exposed wood frames, as some Asian manufactures are still using mortise and tenon on exposed wood frames. Theodore Alexander as one example. But the joinery itself poorly fitted, nothing like what you would expect of a real craftsman.
Sinuous wire springs their using is the drive in type, cant be glued (well it would be a waste of time) just stapled and also its not well engineered as the spring action from a single attachment point does not allow for rotation of the spring when it flexes. Everything else is pretty much standard in high end upholstery. But dont pay extra for bit of miss- advertising. IMHO

I see what Rmanbike is saying about the joinery being mortise and tennon and then corner blocked, triple dowled, glued, and screwed. Perhaps they are using a bit of both depending on the area of the frame. You might want to ask the store for clarification and then let us all know as this sounds kind of interesting.

Regarding the spring some manufacturers put another rail in the front of the front rail of the frame and then this rail is dropped down about an inch. This is usually used with a plywood frame. Then they use a clip called an RJS clip. This clip is shot on with a gun. Some frame shops if they use the rail have a machine that puts the clip on the frame. I haven't heard of any company still using this system. Southern furniture used to do this but I am not sure if they still do this. They do this so you can arch the spring and give you a softer seat. Some manufactuers also then drive the spring into the frame with a hammer. But I don't know of anyone that still does this. I can't see how you could glue in this type of spring. In my opinion the spring action from a single attachement point would be the same as far as durabilty.

Here again I think I would ask for clarification on this point as what they are saying is confusing.

Thanks for the feedback. I found out that the manufacturer is McCreary Modern. Do you know anything about them? I heard that they also make furniture for Room and Board and Crate and Barrel. Thanks again!

McCreary Modern is a department store line.

They build a pretty good product. They generally use plywood frame, maybe some hardwood, no sag spring and stretch webbing and Felxolator. I don't think they do any 8 way hand tied. They have a good blend down cushions and blend down back. I think they use Interstate cushions. The company is still owned by Bob McCreary, who I think is semi retired and as such a family owned company is a plus. Wouldn't be a bad choice in their price range.

Steel has a very interesting characteristic, that its strength is greater when pulled or stretched, compared to when being compressed. And because of the leverage applied in the turn of the wire and the twist associated to just one center point this drive-in type of sinuous wire spring, doesnt make a good choice. As the twists on this point fatigues the wire. More so because all sinuous springs are tempered. Also the pre-drilled (some dont even predrill the hole) hole in the rail becomes deformed over time and I have seen them pop out.
But it can be about 50% faster to spring-up this type of sofa compared to the end of the loop placed into a clip thats attached to the frame. Which I recommend as the best way to spring-up a nosag sofa.

Very interesting