Actually no, at least not Petco unfortunately. I'm not endorsing them selling them this young at all, but I know the animal manager at my local Petco, and she actually puts the new beardies they just get in a tank in the back for at least 2-4 weeks before they put them out for sale, unless her district manager is there in which case they're for sale.
The vendor that ships beardies to them does not go by age but rather length and weight, and the average age when Petco first gets them is 4 weeks old, 4.5-5.5 inches long...It's awful but it's true. I don't know about PetSmart, as we don't have one locally, but Sally complains constantly about this particular vendor, they get all of their reptiles and some birds and small animals from them. So they just tell everyone that they're a month old (4 weeks is a month I guess). It's terrible, but when I got my girl Izzy from her last December (weird story, I caved and took her for my friend) she was only 4.5 inches long and weighed 7 grams...She's fine now, 9 months old and 18 inches, 451 grams, but she was the size of my pinky finger.
It's all dependent on what pet store you're talking about, and the vendors want to get rid of them ASAP to save money...It's terrible.