These blocks use flat models, as opposed to them being arranged in a x or # shape like many other blocks. They float above the blocks they're attached to, which is a bit weird.

This would not be fixable by moving their models down to the exact block, as this would more than likely cause unsightly Z-fighting issues. A better fix would be to introduce dedicated 3D models for these blocks. While this would result in very complex models that may be trickier for the game to render, it would eliminate this odd floating, look nicer, and allow for unneeded faces to be culled.

Redstone dust and lily pads are rendered a lot closer to the block it sits on, and the floating is unnoticable in the former case, so other blocks could be made to look like this to fix this also.

How to fix

The resource pack attached to MC-237445 fixes this issue completely, alongside fixing multiple other issues with flat plane models.