I think the "list value" in the early 70s was very much nominal-only - your chances of getting even half that from a dealer was nil. However, what is surprising is that pre-47 silver was being bought even then at ?twice ?4x face value, in any condition, so whoever put them into circulation obviously didn't realise this.
I do remember the occasional high grade florin turning up, as I was a Birmingham student 70-73, but not in the quantity you saw.
The whole point of florins and shillings being the same size was that their value equated exactly to 10p and 5p, which meant that they could be introduced from 1968 and got the public used to decimals 3 years before D-Day, making the transition gradual and much easier. The cost of production was absolutely not relevant at that time, but when their intrinsic value began to exceed their face value (and remember how rampant 70s inflation was; 1967-68 RPI bore no relation to 1990 RPI) then the Mint took the obvious step of reducing the size of all CuNi from 1990-1997. The old shilling vanished in 1990, and the florin 2 years later, so if the article says "having shillings & florins still around in 1990s was just a bit silly", it's barely even true!
I'm very surprised that Coin News should not understand this.