That still not that what that says, it's what you sent to see. The requirement from government was to improve the air quality in GM to a specific level by 2024. They didn't explicitly state a charging CAZ was required, however they rejected funding for any other option, as the modelling couldn't show it would provide the benefits in the timescale.
Options like massive improvements to public transport were considered, but generally couldn't be achieved in the timescale e.g. new tram lines would take a lot longer. Other options like improved cycling wouldn't change the air quality anywhere near enough without getting to Dutch or Danish levels of cycling, which takes many years to get people to do.
The only way to achieve the air quality improvements required was to remove the source of the pollution i.e. the most polluting vehicles. Asking people to get rid of them wouldn't help, so the only option is to penalise people who have them to convince them to change. If you've got some better ideas to improve air quality, I suggest you go speak to government as there will be a lot of money in it for you, as the only choices appear to be ignore it and leave us all breathing poor air or charge the most polluting vehicles to get them off the roads.
I think the choice of charging vans was wrong, as, at the time, there were no alternatives other than expensive, nearly new diesels, but they chose them rather than private cars as they thought it would be more acceptable politically. COVID may have helped the problem, as changed working patterns means less cars at peak periods, plus it allowed more electric vehicles as it was right at the point this like the Tesla 3 and ID3 were starting to appear on company car lists.
We may therefore no longer need a GM wide CAZ, but that doesn't change the fact that we did back in 2019, otherwise we (the mayor, & the 10 authorities) would have been breaking the law.