For some reason this differs from the master branch, and looks potentially half-finished (isn't a valid loot table - is shaped but uses shapeless ingredients instead of a key):

https://github.com/MehVahdJukaar/Supplementaries/blob/a7e875856ee2cdf2680de312e63be23ede3b7063/src/main/resources/data/supplementaries/recipes/flax_block.json

(it ended up in the 0.17.7 release on CurseForge)

oh yeah I messed up lol

fixed in 0.17.8