When a player harvest a plant with the relevant magnet ring, or a certain machine (uncertain on the specifics) in Industrial Foregoing harvests a plant, all of the drops are consumed and no seed is found. Thus, the block state is never replaced -- meaning you can infinitely harvest some plants.

I posted a video of this on the BM discord a while back.

InsomniaKitten was the one who worked out precisely what was happening (i.e., all drops being eaten). They suggested replacing the block state regardless.

My concern with that would be things like Mystical Agriculture's plant-types for essences or Extra Utilities 2's ender lily seeds could thus still continue to be "duplicated" (even with the state changing), as you would get the seed, and then break it and get another seed.

My thought to resolve this would be a high priority event handler that looks for a seed before other mods have a chance to consume all of the drops. How this would fit in, I have no idea as I only have a passing understanding of the code -- otherwise I might've attempted a PR.

If this bug report makes no sense, please blame my brain which is currently non-functional.