Vanilla loot tables are hardcoded to check for minecraft:shears, so using wooden shears on many vanilla blocks such as leaves or tall grass will drop seeds and saplings instead. Forge might need to add a forge:shears tag to fix this.

Fixed in 1.15.2 release https://www.curseforge.com/minecraft/mc-mods/sbm-wooden-shears/files/2954828

Might back port to 1.14 if there is enough demand