"we don't have time for that..."
Was Joe Biden's answer to why there were so few Federal prosecutions of people lying on the 4473 form.
It very well may be that they don't "have time" to bust the little guy, TODAY.
Doesn't mean its ok to break the law, only a comment on your odds of getting caught...today.
IF the people running the agency decide to change the focus of enforcement (which could happen at any time, and under any administration), the odds of you getting busted for breaking the law, will change.
The ATF has a long history of changing its mind about what is and isn't a crime, and it is also subject to being ordered to change its rulings and enforcement priorities.
If you count on a cop/agent's advice as legal bedrock, you could find yourself on very shaky ground. They might honestly be telling you the truth as they know it, but that's no guarantee they are right.