It’s not a typo. It was a deliberate decision by congress to give subsidies and have the employer mandate only in states that created a state Obamacare exchange. It was the hammer to force states to have exchanges.
The statute is utterly clear in that regard. Jon Gruber, architect of Obamacare, said exactly that in 2012.
When only 14 states have adopted state exchanges, the IRS made up a rule that expanded the statute to state and federal exchanges. The result of that rule is a $600-$700 billion expansion in the federal budget. The IRS has no authority to spend money etc. But it did, big time.
Today’s narrative is that the clear language in Obamacare must have been a typo. That is a deliberate lie. Jon Gruber is now telling the lie de jour along with the rest of the administration and democrat party.
Congress didn't write it, I don't even think they read it.
Some leftwing "think tank" probably wrote the thing.
I don't think Congress deserves any credit.