I don’t reckon that the leaks are accidental either. The Biden Administration waited until the tide of public opinion turned further against Russia. They waited until the rest of the West had committed MBTs to Ukraine before allowing this to be leaked. There’s a message being sent here.
Assuming this is an blog from Sy Hersh and it's not made up by Sy Hersh and it's not made up by the person Sy Hersh interviewed (all of which might be possible and can't be easily claimed to be unlikely (or likely)):
The US still doesn't need to send a message now and it's still not profitable for them for the article to go public now.
More likely is that both Sy Hersh and the informant didn't want to risk it before. E.g. due to fear of personal consequences or due to fear of causing political consequences in ways they don't want to cause.
Wrt. the the normal citizens in the EU the US doesn't need to send a message, nor would it be received. Wrt. politicians messages already have been send clear enough.
