I mean...... when I get on a flippn airplane all I have to do is either show the boarding passon my phone or show one that I just printed at home on my cheap ass printer... If that's good enough to fly then it should be good enough for anyone to get an air fill or a boat-ride to a dive spot...
I totally prefer the e-card......but when I travel I still keep a paper print out of any needed certs... Usually I just show a pic of an AOW and NITROX cert and never been questioned..
Here's a screenshot of what comes up on my phone when I open the PADI app.