Bug:

Crops in minecraft bedrock are very special blocks because of their properties: They are not considered full blocks, can be destroyed by liquids, don't support gravity blocks on top of them, don't allow for snow layers to build on top of them, etc.

And, grindstones (minecraft:grindstone) are blocks that need other support blocks so they can be placed. The same behavior is observed in bells (minecraft:bell); If their support block is removed, they break. And, if you try to place them against a non-full block, the game does not allow it to be placed.

However, unexpectedly, grindstones can be placed on top and on the sides of crops: Carrots (minecraft:carrots), potatoes (minecraft:potatoes), beetroots (minecraft:beetroots), wheat (minecraft:wheat). This behaviour is not seen in bells or other similar behaving blocks, therefore, I assume this is not intentional behavior, so, I decided to report it.

Disclaimer: I didn't tested with melons and pumpkins stems. 

Steps to reproduce:

1. Create a normal world either in gamemode survival or creative, or just a flat world in creative gamemode;
2. Acquire a grindstone block, acquire a hoe of any material, acquire either a potato, a carrot, a wheat seed or beetroot seed;
3. Use the hoe on dirt close enough to a source of water to create a farmland block;
4. Plant the potato, carrot, wheat seed or beetroot seed, (either one you have) in the farmland created;
5. Try to place the grindstone on top of the planted crop, or in one of the empty sides of the planted crop;
6. Grindstone is placed on the crop block. 🟥

Expected Result:

The grindstone would not be allowed to be placed on a crop block since it is not allowed to be placed on non-full blocks, specially, "special" blocks such as crops similarly to the behaviour observed in bells.

Observed Result:

The grindstone was placed on the crop, visually floating, on a block full of properties which we don't expect a grindstone to be attachable to. And, of course, whenever the crop is harvested, it also breaks the grindstone, but, at least, the changing growth stages of the planted crop don't seem to affect the grindstone.

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(Miscellaneous) How the bug was found:

I was creating a mod of my own adding crops and foods, but, when coding the crops, I was also testing my own crops against vanilla crops. Based on that, I start testing blocks, like gravity blocks, ladders, fences, pots, painting, item frames, liquids, etc, and trying to replicate vanilla behavior with my custom blocks to the best of my hability using scripting API. So, upon scrolling the creative list, testing, comparing to vanilla behavior and verifying what I needed to code, after a long time making tests, I tested the bell, and.... for my surprise: the gridstone. As expected, the grindstone on my custom block, treat it as a full support block, so it did the bell, but, when I compared with the vanilla wheat planted on the side, to my surprise, the grindstone also treated it like a full block, which didn't happen with the bell. Generally, vanilla crops are very special and this was not normal, so, I thought this was strange, so, I tested with carrots, potatoes and beetroot, and the same happened. So, I thought the grindstone placement weirdness was a forgotten bug and decided to screenshot and report it here.