I arrived MEX April 1 and received the slip with the QR code going through the E-gates. I never got a stamp in my passport. I tried in vain to obtain the online Digital Multiple Migratory Form as it's stated pretty firmly that you MUST do this. Well, I didn't. On my return, April 11th, I had the original QR coded slip in hand that I got from he E-gate upon entry. No one asked for anything. I did online check in and had carry on, so I didn't have to go to the check in desk. I asked at the Admirals Club if this paper was needed and they said it wasn't necessary any more. No one asked for anything at boarding.