I agree, but that’s takes more skill that most people are capable of. Most people would have to seek out a forger to get a fake vax card. But if they can just print something, then anyone can make their own fakes.
I see this more as a problem for the vax sites. With how tough it is to get compliance, they are acting irresponsibly by creating official documents that literally anyone can print at home on paper they get from the office supply aisle at their grocery store. Public places like restaurants will have to have policies that literally anything is acceptable instead of requiring the CDC vax card. Vax paperwork given out by vax sites should be CDC cards, not random printouts on A4 paper.