2003 Chevrolet Impala Grinding Noise

Nope. The upper strut mounts can make noise but only when you're turning the steering wheel. The entire weight of the front of the vehicle is on those two little bearings, and most of the time there is no easy way to inspect them other than to disassemble the strut assemblies. Typically, when replacing struts, that's when wear and damage is first realized, and the mechanic has to tell you more parts than first expected are needed.

The noise can be a creaking noise, but much more commonly the bearings bind from dirt and rust, then you'll hear a snapping or banging noise when you turn the steering wheel. That most often happens when the vehicle is standing still. When moving and turning the steering wheel, road bumps and vibration help the struts turn without as much binding.

To test for a binding upper strut mount, reach over the top of a front wheel and lightly wrap your fingertips around an upper part of the coil spring. Have a helper slowly turn the steering wheel. You should feel the spring rotate smoothly with the wheel and tire. If the upper mount is binding, you'll feel the spring wind up and build tension, then suddenly pop free and turn.

The noise you described is never normal, and while it very well could be not a safety issue, you want to know what it is and you want it fixed. Part of doing an alignment can include readjusting how much a wheel is tipped in or out on top, and changing that orientation will cause some other suspension parts to sit just differently enough that a half shaft could rub on a dust shield, and maybe only when the engine rocks from acceleration or coasting. Another common cause of grinding on some car models is a bent splash shield behind a brake rotor. If necessary, have a different mechanic listen to the noise and do an inspection.