So I dug up this WWW, q77. Forager duplicated it. The other seeds are from the area, so i know it maxes out at q45 or so.
It seems likely that there are q77 turnips somewhere in the game, but poppies are very slow growing, and its odd that they are both the same q.
My assumption is that the code checks for chance of crop q, sets that as the quality and type, then forager inherits the quality level, but randoms the type based on the related biome. You can see in the picture i received many poppy seeds from this area.
I dont know how rare both mechanics triggering at once is, but I imagine there are others who have had this happen as well.