API/Modloader
Fabric

Describe the bug
Overgrown netherrack and mycelium netherrack cannot be spread to create more of them or to repair bald spots in the ground.
When bone meal is used on netherrack that is next to either, it is consumed, and green bone meal particles are created, despite nothing actually happening as a result.

To Reproduce

• Place overgrown netherrack or mycelium netherrack surrounded by netherrack.
• Run /gamerule randomTickSpeed 999 to set the random tick speed to an absurdly high value. Vanilla grass and mycelium spread absurdly quickly in this environment, but overgrown and mycelium netherrack do not spread at all.
• Use bone meal on netherrack that is adjacent to either of the above blocks in survival mode. The bone meal is consumed and green particles appear, but nothing happens.
• If you do this in creative mode, the use item hand animation still plays and the particles are still created, but the bone meal is not consumed, as the player is in creative mode.

Expected behavior
It's up to you whether overgrown and mycelium netherrack should spread on their own, like grass and mycelium, or with bone meal usage, like nyliums. Vanilla behaviour would suggest the former, but then you'd need some way to prevent these blocks from overgrowing nether wastes biomes, should a glowstone gardens/wailing garth/etc. generate next to one. This issue I believe is why nyliums do not spread on their own in vanilla.
If you choose to have them spread like grass, and find a solution to prevent them from overgrowing nether wastes biomes, then using bone meal on netherrack next to these two blocks should be impossible.
If you choose to make them behave like nyliums, then using bone meal on netherrack next to either block should turn it into the that block, or turn into a random block if it is next to multiple nylium types/overgrown netherrack/mycelium netherrack.