Interesting! I bought the 9L mk1 Cambrian from SJS at their sale price, but I seem to have had an upgrade.
Ha, I did say it was bewildering! Looks like you got a bargain.
I imagine the roll top and extra material means it holds the shape better, though at the cost of weight, as with all things there's pros and cons, not sure which I would have preferred but I'm happy with mine.
Just had a look through the Last Chance stuff, not really surprised they're rationalising the cotton saddlebags, I think you'd have to really like their aesthetic to choose one over the modern material versions.