If a block does not require a tool by default, it cannot be given one via datapack tags. The block will be added to the relevant tags if the files are added, but the behavior of the block is unchanged.

Steps to reproduce:

1. Create a datapack.
2. Add a block that does not require a tool to drop, such as a Rail or a Piston, to the block tag "#minecraft:needs_diamond_tool".
3. Attempt to break the block with an iron pickaxe in survival mode.

Expected: The block would not drop unless using a tool of diamond or better level.

Actual: The block will always drop.

In this example, I used rails because they mine faster with pickaxes, but by default do not require any tool. I have also observed this bug with Pistons, as well as Oak Logs (mines faster with axe).