Yeah...You're good to go
I was fretting over the same issue but not from Seedsman...
Just go pick it up cause they have made an attempt to deliver...(mine they didn't so I was scared but still they delivered without Signature in the mailbox)
Seedsman is the Customer...to the Postal service. YOU are the customer to Seedsman so
Seedsman like all international seedbanks request signature now, some USPS will follow through as they should and some won't (like mine and just put it in the mailbox)
Regardless, you are safe, they all pack them to the point that delivery agents can't even tell it's seeds. And as Hydrokid stated..they would have stopped them at Customs and the latter would be you receive a letter from USPS telling you to provide proof that you can obtain what's in the package, by bringing documentation. (I received that on some T6 I ordered which is illegal without a prescription)