@BobKamman 

We can't decided if it's wrong, or right, until the OP discloses how it's marked. 

NOW, we know, because the OP has responded.

From first hand experience, if the retirement box IS marked even if incorrectly, the IRS will disallow the IRA contribution.  

The OP, and the OP's client, need to prepare for battle if the IRA deduction is claimed.  

I agree an amended W-2 could just muddle the water, and lord knows it won't be processed before the 10.15.20 deadline in any case.