Heres how it works: Till grass, equip watering can, hold right click on the tilled dirt, and drag to cover more tiles, you lose stamina without having to water them! :O
So, I may be missing something here but I thought I’d ask. I haven’t been able to replicate this yet. First, when you say drag to cover more tiles what do you mean? It isn’t possible to drag across tiles to select them. I’m assuming you are just talking about holding down right click to hit multiple tiles but I’d like confirmation if you don’t mind.
Next, when you say your stamina goes down, are you talking about immediately when you right click? Because that is intended. Once the game sees that you right clicked and you can water a tile it subtracts the stamina right away. You are already locked into watering a tile at that point so you don’t really lose stamina its just deducted in preparation for watering. Admittedly though it would probably be better to deduct stamina as you actually water tiles rather than before hand.