Looks like damage from being scored with a metal tyre lever or gritty rides with tyre slipping on a relatively narrow rim. Seen that on plenty of my Kenda DH tires, but presume not with this tyre as they come on/off with no tools on my rims.
I easily run a full season on a single front MKII, the rear tyre shows much more sidewall wear and I need to replace my rear once to get through a season..
I figure the rear tyre wears faster as I dont get to choose the best line for the rear as I can for the front and drag it through the rocks etc as a result.. I get threads showing relatively quickly but nothing like what your picture shows. I also replace sooner than necessary as I’m anal and don’t like things to look tired 😉
I run at 20-25psi so get some significant sidewall deflection.
The rubber overlay is pretty thin on some tyres.. gets thicker with protection sidewalls, RTR and obviously UST versions.
I’m pretty sure the tyre pictured is also old stock.. not current generation rubber as far as I can tell from the logo. Is it a wire beaded tire taken off a bike with that tyre as oem fitment? Hanging in the shop for a while before you picked them up?
I’d still go back to the shop.. the presence of the mold riser knobs are a good sign of relatively little use. See what they say.