We did this to avoid people from getting scammed
Yeah, back in 2006, to prevent getting scammed with the "Unidentified Herb" trick, we said "Buying Unids lvl 40/whatever and above" and filled our inventory with 1 of each of the noted herbs you wanted and the rest with junk. If the trade didn't go through, the person was giving you bad herbs.
Grimy is love.