fiat here means (roughly) government issued, I think

that's the correct distinction, but the poster I was replying to was trying to make some arbitrary distinction.

I don't follow? They are saying that in order to run a business in which one sells goods or services for cryptocoins, that in order to pay for one's business costs, one must spend fiat,

and that therefore, someone selling goods for cryptocoins, must, in addition to using cryptocoins, also use fiat currencies (because most of their business expenses can only be paid in fiat currencies).