Surely most drugs could be sold in small enough envelopes that you don't need parcel postage. I know when I was using DNMs most packages were a simple large letter stamp stamp which covers 35.3cm x 25cm x 2.5cm and a maximum weight of 750g. So I doubt dark net drug orders would have been the trigger for this sort of change.
As a consumer of black market peptides (formerly gray, thanks RFK) there doesn’t seem much of an attempt to hide it nor does it appear that anyone is intercepting them. The only package I lost was due to the LA Railroad heists.
