If he performed his services in the US, the income is sourced to the US.  Getting paid by clients located in a foreign country does not make an income foreign source.  If he lives in the US and performs services remotely, US is his tax home.  He would not be eligible for foreign earned income exclusion.

What kind of foreign tax did your client incur for working remotely?  Did your client set up a foreign entity, conclude contracts using that entity, and bill his clients through that entity?  Hope not.  If so, there's a lot more your client might have to worry about.

This is not an input question.  This is a structural issue and a technical question.