that's a design flaw and on Tesla. is the owner expected to lift the car, remove bolts, take of panels., shake it out and then re-install regularly?
I dunno. In the Spring, I always lift my car, and remove the snow tires, or if I don't have snow tires, I rotate my tires. Either way, I always do an inspection, check the pads/rotors, lube the pins, look at the suspension. Doesn't everyone?
As for the undertray, that has only been in recent years that vehicle manufacturers have been using under trays to improve aerodynamics. My Chevy Bolt had under trays, and yes, they filled up with pebbles, worse than my Tesla. How do I know? I vaguely recall hosing it out every Spring.
As for the Tesla, I was actually looking for pics of our muddy road in previous springs, but didn't find any. Instead, I found a video of me knocking on the underside of my Tesla:
That's April 5, 2019, 4 months after I had gotten my 3, and I must have seen a YouTube video of all the dirt that accumulates. I tapped and no, I didn't find anything worth worrying about, so no, I did not remove my panels and shake anything out. In 5 Springs, I've never taken off the panels to just remove dirt. Only 4x: twice for 2 alignments I have had done. The tire shop did that. I always get an alignment after I put on new tires. And, once, when I removed the front panel, to replace it with a metal one. And once, when I tried to figure out why I was getting an inverter motor whine, so I took off the front panel to tighten the inverter ground nut.
All 4x, I did not find enough dirt to get all worked up about. I think if you have unusual road conditions, and if you can hear significant dirt from tapping, or if you can see significant dirt, from the wheel wells, then by all means, you can remove the panels and remove the dirt. But no, it's not required at all.