I'm not sure what you're saying here. There were generally five walk-up return fares available on the GN network:The announcement on the Great Northern website, and the notice in the photo linked from entry #1 above, only mentions weekday Super Off-Peak fares being withdrawn, which could be taken to imply that they are still available at weekends, but if you look up a weekend journey on any of the affected routes on the GN site it doesn't advertise a weekend Super Off-Peak Return as such, but it quotes a cheaper Off-Peak Return fare that on weekdays.
For example for Shepreth to King's Cross, the Off-Peak Day Return on weekdays is £31.40, and at weekends it's £21.10, but brfares.com still quotes the £21.10 as a Super Off-Peak Day Return available only at weekends.
Also, for some journeys such as Shepreth to King's Cross, Advance fares are available but the difference in price of two Advances compared to the cheapest return fare is often minimal.
Anytime Day Return
Off Peak Return (return valid for 1 month)
Off Peak Day Return
Super Off Peak Day Return
Super Off Peak Day Return (Weekends only)
The Super Off Peak Day Return (highlighted red above) is the one that has been removed. All of the other fares are still currently sold.
The weekend version of the Super Off Peak Day Return is cheaper than the version that has been removed.