Are internal recruiters (sales people) commission based? Seems strange.
No, but lots of firms (this wasn't Amazon) hire external recruiters who are commission based, usually a percentage of salary for each candidate placed. Some also get "right to represent", where you can't apply through the employer directly once you've started a process with the recruiter.
Which makes this utterly weird - it was literally a matter of giving up (potentially) several grand by not forwarding an email.
I have no idea how a commission-based business manages to do something like that.