Wouldn't surprise me if these re-arranged dates were already being held for insurance purposes - especially with the additional dates they've now been able to add - in case the initial dates had to be cancelled for some reason. Although who could have forseen Covid.
I wonder if for legal and contractual reasons they're then obliged to move to these dates even if the feeling is the Covid situation may not have changed enough by then? The question then is what options are left open to them if these dates then fall by the wayside. Will there be another set of dates now in place as further insurance or will they have to pull to the plug?
The idea of reverting to stadiums might be a good one but then availability and number required would become a factor to cater for everyone with an existing ticket without having to scrap the whole tour and start again.