We are talking about adding it to farmland so we really care about yields and safety.

Possibly. I am not familiar with the sort of basalt they are using here.

It may very well make sense under those conditions.

Olivine is in ready supply as a by-product from the mining industry. There are piles of it laying around (which don't have the same effect as spreading it out) although they do need to be transported to projects.

By-product is the word I was looking for. Hopefully there isn’t a need for primary production