Yes, I remember crusty roses on my Bday cakes when I was little as well. Crusty on the outside, soft and creamy on the inside. Mmmmmmm
As Norcalbaker says, it all depends on the different measurements of ingredients and the types of lard/oil/butter used.
If this was a true old fashioned bakery, then they probably used a small amount of shortening with a large amount of butter in their buttercream. This crusts very well. A higher ratio of powdered sugar to pure shortening gives the same results, but the taste is a bit different. So yes, it all depends on the recipe they use or used.
But as the years go by, different people work in the bakeries and recipes change. Even if they use the same standard recipe, I'm sure that things aren't measured exactly............as how I did when I was working in bakeries back when.
But, in all logic and reality...............a nice crusting frosting really depends on how long you let it "dry". The longer you let it sit out, the drier and crustier it will get.
I've had people complain about some of the buttercream I've used in the past, simply because we weren't allowed to make cakes ahead of time, we had to make them in time for the customer to pick them up. So the cakes I decorated with buttercream never had a chance to sit around and get crusty, and they people would bring them back and complain it wasn't buttercream. And I would have to explain the whole thing to them.