All Avanti-priced Off-Peak Single (Online) tickets [previously known as Saver Half] were removed from sale. The normal Off-Peak Singles were cut to 70% of the equivalent Off-Peak Return.
Without access to the figures, and with the intervention of lockdown, it's difficult to say whether there are more winners than losers with this change. The figure of 70% comes from one of the commitments the DfT wrote into the Avanti franchise agreement.
GWR recently made all their Off-Peak Singles half the price of a return (well, the period return at least) in the area surrounding Bristol. I suppose it's one of life's mysteries why the DfT saw fit to introduce single leg pricing there, but not on the WCML.