It just makes it harder to take on debt if you don't control your own currency as a sovereign state. EU countries are a political union but not a clear fiscal union, with their own treasuries but also the ECB calling the shots and it means that member states can have sanctions imposed on them, like Greece for example.
He literally said it's the MMT. Lmgtfy: https://www.investopedia.com/modern-monetary-theory-mmt-4588060 and it doesn't even say that companies can't get loans.
It just makes it harder to take on debt if you don't control your own currency as a sovereign state. EU countries are a political union but not a clear fiscal union, with their own treasuries but also the ECB calling the shots and it means that member states can have sanctions imposed on them, like Greece for example.