I grew up with the Smurfs cartoon and was a big fan as a kid. When I became aware of these books a few years back I started collecting them. I've owned each in grades ranging from incomplete to slabbed 7.0. I've also sold copies to prominent national dealers who are well aware of what these are. I agree with the sentiments above that these are legitimate keys, or at the very least, issue 1071 is a key.
With that said, I suffer under no delusion that these books are rare, as that term is generally accepted. Relative to lots of Golden Age books, surviving copies of which may not exceed a few dozen, thousands of surviving copies seems like plenty to fulfill demand.
Regarding the census, low numbers may simply reflect demand rather than actual scarcity. See, again, many Golden Age books with as few as zero copies on the census.