My experience

I was the I485 direct beneficiary (EB2 NIW based) and after my I485 was approved, I had to get my passport stamped before I could get my GC.
My wife was the derivative bemeficiary. She got a letter saying that her GC was being made (Welcome to USA Notice). She also got another letter stated that if she needs a stamp on her passport, she could bring this letter to local USCIS and get her passport stamped. She got her GC directly from service center without stamping her passport.