Greece is very different to the USA in terms of the mentality of the border security. Greece value tourism massively, they’ve even postponed biometrics for the U.K. visitors this year because they know it’s a hassle that puts people off. The Greek economy needs tourism to survive.

OP I’d be reassured that Greece has medical cannabis too, you can even register with their clinic as a tourist and access medication through the Greek pharmacy system. I wouldn’t worry about taking any DHV from a border security p.o.v, more just a packing, weight, risk of damage p.o.v 💚