There really is something weird going on. I went trading in south-eastern Driik in early Seedtime/May (my base is in northwest Driik), and upon entering one village, discovered lots of peas and rye for harvest - I immediately saved the game and made a copy of my character folder, then reloaded the save - and all the harvest was gone! The field is now completely empty of rye and peas - just some dog pipes, milkweed and clayweed here and there (aren't these also out of season?). Seems like the logic is something like this: when you first enter an area where something has new sprouted, the game shows it as fully grown and harvestable - however, if you reload, or move to a new area where similar crops are growing, the game catches up on unseasonal crops and from then on, it shows the correct harvest time. I've attached a screenshot of unseasonal milkweed - these seem to persist even after reload - sadly I didn't think of getting a screenshot of the unseasonal rye harvest...