When using a piston and naturally generated water, it is possible to trick the game into thinking that that block was naturally generated, allowing for the effects of the skyroot tools to be used. obviously this only works on blocks which can be mined by skyroot tools in the first place.

I just tested this on my own. To reproduce the issue:

Place a block of dirt (or anything minable by skyroot tools)
Place a piston next to the block facing it
Activate the piston to move the block
Mine the block with a skyroot tool

By moving the block with the piston, it will trick the game into dropping two dirt blocks instead of one, which means this is an item duplication bug.

Yep, that's basically it, Use a piston to push a skyroot mineable block down into specifically naturally generated water. And then the game will be tricked into thinking that the block is naturally generated, no matter what it is. The main conditions are, needs to be pushable, and needs to be mineable by skyroot. If the naturally generated water is an infinite spring, then the process can be repeated infinitely, allowing you to dupe a lot of annoying to create blocks like concrete.