Just used SSWUs for the first time as freshly minted Elite. Called in to to book the upgrades four days before the flights and got a confirmed upgraded seat which printed on my advance check-in BP.

When I was at the gate, it didn't look like the GA was expecting me to hand them over the SSWU cert - but they took it anyway. Is there something that flags them to ask for the cert? I see CERT in small letters on the BP, but I'm wondering if I just show a BP that says seat 1D, what happens.