A couple of things came to mind reading this post. First, I recall noticing the same thing the first time I opened my Eureka Mignon Specialita. The screws holding the top burr carrier in place were slightly rounded off. Nothing major, but it was a bit of a surprise to see damage to the screws on a new grinder. Maybe someone in the factory isn't using the screwdriver properly?

Second, I would be really careful about replacing the screws with Allen or hex screws. Phillips screws cam out by design, which limits the torque one can put on them. The burr assembly, on my Specialita at least, is aluminum, and I would worry that a more positive screw head might encourage over-tightening, which could strip something a lot harder to replace than the screw.