Indeed, it has been discussed many times. But I don't remember any discussion on attribution rights. If GS replaced GPL text with their own header they presumably deleted names of the original authors. I wonder if those authors could (collectively perhaps) send a complaint to GS and ask to restore the attributions?

To be pedantic, the GPL doesn't actually say anything about the contract between an employer and employee. While I highly doubt the Goldman Sachs employment contract is anything other than work-for-hire, meaning you're still right, it's not impossible for a programmer to retain copyright of code they write (eg, any code you write on your own time on a computer you own).