That is an assumption. In 2019 they audited about .29% of taxpayers with incomes under $200K. I've heard it both ways but I wouldn't just assume they'll be fair or it will make sense. I'm pretty sure auditors are incentivized to recover as much as they can. A very good friend of mine was audited and they initially went after him for some ridiculous amount. He got an attorney who researched then negotiated it down to about half, but about a third of that savings went to attorney fees. What kewl says about applying for gov benefits sounds about right. All I know is I didn't care for a USCIS agent interrogating me despite the fact I had excellent documentation.
I would assume this: It won't be fun and it won't be cheap.