We flew IB MIA/MAD last week and if I hadn’t asked at check in if he wanted to see my QR I don’t think he would have. Not much difference on arrival in MAD.

From my experience here are some things that I learned. I submitted my SpTH and then my wife’s a month before departure using the same email and when I tried to complete them hers went right through mine would not take. I finally redid my SpTH and added a zero in front of my passport number and it took.
Also my CDC card did not have my full name including Jr as my passport does and they didn’t care at immigration or where they checked our Covid documents. I expected that to happen at immigration but it actually happened at the main terminal T4 before baggage

Hope it helps