> it's been well known for a while that statistically, if you are admitted at a weekend, you are likely to have a poorer outcome
I think this is the nub of it. Resources are limited, so the way this could work is for outcomes from Monday to Friday get a bit worse, freeing up resources so that outcomes at the weekend improve. The average outcome across the week then stays roughly the same, but patients wouldn't be disadvantaged by being admitted at weekends versus weekdays.
Average outcomes could be improved by improving productivity (where productivity is defined as successful outcomes per pound spent) or by providing additional money/resources, but I don't see the proposals mentioning either of these options, simply re-allocating money/resources to provide better outcomes at weekends. Therefore this must be at the cost of weekday outcomes.