Dude I don't even know how the stocks work at my current employer. Can't force you to believe I got an offer there and I'm not forwarding you my offer letter...so choose to believe me or not.
Putting aside the very rude "dude", it is not a matter of how RSUs work or do not work, more simply they never talk about RSUs because they do not give RSUs.
As I said, you never got an offer or you did not pay any attention. It is fine either way, of course. No need for any letter.