I'm not sure which year they added the extra protection ie skid plate but, if you are super worried about it I would install a aftermarket skid plate for it. I am the only one that I have ever seen that would admit to putting a hole in a def tank, did it on my 11 truck!!! I found a plate made by Ore-Fab (no longer in business) for $139.00 put it on and did not worry about it again. My 19 truck seems to be much better protected than the 11 was. Just my $0.02 your experience may vary.
I have not done it but have seen 2 done on our ranch in NM. Going to catch a lot of flak for this but it is the truth. Love my 2020 but where I go the 2019 and older not a chance. I used to send feedback to GM on surveys that I love the trucks and the Duramax but the DEF tank I was too smart for that. Do not want to get stranded 27 miles from a gas station and 12 from a paved road.