OK, yeah. They can gather nuts (non-plantable seeds). But I still don't understand FantasticDorf's "seed bank for herbalists ... with free booze as a byproduct" paragraph at all. Is he just putting a seed stockpile up there so the herbalists can drop off their nuts more quickly, and get back to more gathering? If so, I'm still dubious, because they tend to carry lots of plants/seeds around with them for a long time before dropping them all off en masse. (This isn't like 0.34 where dwarves could only haul one item at a time.)
Apologies if i haven't articulated myself fluently.
The chain of production for my herbalists are that they go off and collect plants, i return said plants which then get used up any which way by my dwarves (personal preferences for instance make often what i bring back a hit at the dining tables without even being cooked) with the produce secured in a close by stockpile. All the goods are indiscriminately processed for the seeds which are then funneled by haulers into my no-barrel all bag seed bank.
Herbalists -> Gathered Plant Stockpile -> Processing (still/quern/workshop etc) -> Seeds gathered for bank -> Bags are ready to be collected for future farms without getting stuck within a barrel or applying another bag.
Should i require above ground farming, i will have a ample supply of seeds i can use. The processing byproducts are eaten and drunk by my dwarves. Quite simple really. Clear out the map of gatherables each season, churn it all up, collect the seeds, sit back and relax no worries.
Better bags, more profit from a surplus of seeds. What more could you want?