Here's how to tell, far easier: take the number of people receiving checks in that age bracket. From what I read, it was 44,000 ish, but I can't verify that. If it's not - it's still going to be a number far less than 20 million.
Do all those people have correct data? If not, correct that. If they do, then there's no fraud.
And even after that, even if the data is incorrect, it doesn't mean there's fraud. You have to go case by case to check if they're actually being collected and not just sitting somewhere.
So .. yes. There's potential for fraud, but we're not going to (accurately) know about the scale for a long time, and it's definitely not going to be on the scale of 20 million recipients.
Do all those people have correct data? If not, correct that. If they do, then there's no fraud.
And even after that, even if the data is incorrect, it doesn't mean there's fraud. You have to go case by case to check if they're actually being collected and not just sitting somewhere.
So .. yes. There's potential for fraud, but we're not going to (accurately) know about the scale for a long time, and it's definitely not going to be on the scale of 20 million recipients.