Where does it say that this caused the outbreak?
It seems DEFRA would like us to think it blew across the north sea, but though that’s vaguely possible it’s far less likely than it transferring from imported trees.
Woodland Trust have made comment on this- they’ve been investigating their supply chain and discovered that they’d bought saplings that were officially british produce, but which had been grown abroad.
Certainly isn’t compatible with the idea of closing forests to stop spread! TBH you can’t stop an airbourne disease like that, this isn’t like sudden oak death.
Seems likely that it’s far too late to do anything about it sadly. But at least ash spreads and grows fast. The government response could cause as much damage though- I remember with the “great storm”, our local wood took more damage being prepared for replanting than it did in the storm!