It’s proxied. The idea is they buy a premium account on the file hosts they want to support, then request the files using that account on their end and they pipe back the file to you at premium speeds. They have to proxy it or it would be trivial to see that some accounts request files and it gets downloaded from another country.
Then they can resell that as “works with those 24 providers” for cheap and pool possibly hundreds of users per premium account upstream and generate quite a bit of profit.