> But it doesn't address first mile to hub. Can a bumfuck workshop in a hamlet deliver in Greece deliver to warehouse in Poland across multiple jurisdictions for peanuts?

Yes, unless they're doing so at a ludicrously small scale. Sending a 20t lorry load from Thessaloniki to Warsaw will cost less than 6000 euros. I suspect it can be done for around 2400, but I don't know the route very well.

>My understanding is EU first mile is fragmented/slow if you rely on national post and expensive if you rely on private couriers.

Yes, it sucks at ultra-small scale. But that's really what that is. The private couriers have super attractive volume pricing, even 80% off public (consumer facing) rates isn't unusual.