According to the wiki, only the planting of the seed matters. The harvest can be done by anyone.
Harvesting is not as important as planting, as the size of the stack harvested is not affected by the harvester's skill level. However, harvesting crops does give experience, and if other dwarves are harvesting, then your planters will not gain experience as quickly.
This has been my experience as well.
It's true that the Wiki does have that about farming, and um, I guess I might have had it wrong all this time. But's that what I was seeing... Too bored to test but it would be good to get first person confirmation.
Trappers are definitely worth testing, mine were quite rudimentary. There are several tasks involved- the trap-making task, setting traps and chasing vermin around the fortress. Never bother with setting traps myself - usually forgo the trappers as well.
I'm trying to keep the quality column to mean 'improved results'. As there is no such thing as a masterwork mushroom, it seemed weird to put it in that column.
Sure but there's no such thing as a masterwork pacification either. And getting [6] Plump Helmets is a vast improvement on getting [2] Plump Helmets (even x3). To get your [30] Dwarven Wine from [2]x3 you need 3 times the labour (planting, harvesting, several hauling jobs, barrels, brewing) and that's a lot of difference in results. Dare I joke about quantities having their own qualities?
Anyway looking forward to your science.