So basically they’re saying that dress codes are okay, but not dress codes based on religious beliefs. (And these rules don’t require long sleeves for example, so they are not exactly pushing “Hasidic extremism”.)
And these stores serve everybody, not just Heimishe Yidden, or Yidden at all, for all those assuming otherwise, although most Jewish stores have mainly Jewish clientele.
However, I believe these signs were the result of a prior discrimination lawsuit by an employee of one store (and were probably made in conjunction with legal counsel) to show that the same requirements are expected of everybody and thereby avoid further legal trouble.
Obviously, hate transcends logic, hence the lawsuit.