We don’t have data and what if they convert back into fiat? Would you say that foreign workers who get paid in USD and send money back home only use USD as a ponzi?

You don’t need data to see plainly that the vast majority of goods are obtained with fiat. As such, someone selling goods for crypto has no choice but to use fiat as well.

I really don’t get your distinction between fiat and crypto

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).