I'm not really worried. It's just something I'm noting that was new.
The OEM/HPS never did that on my 1st gen and the OEM/HPS never did that on my 2nd gen. The 5.0s do seem to have tweaked the thin steel backing plate behind the pad material thick plate. Ever manufacturer probably does that part differently and that might just cause something I hadn't encountered before. I was mainly chalking it up to them not having been abused yet, still having factory-fresh chamfer, etc.
The noisy guy is on the driver's side, and I did have to tweak one of the spring clips on the driver's inside pad...so there's some correlation there.
2011 Graphite Mica Mazda3 sSport 6-spd MTX