I'd bet it's not immune to small pellets of lead or steel flying towards it at around 1000fps.
Or a rock.
I'm less accurate with the rock though...
This is one of those articles that would have made me go "WOAH, that's so cool, the future will be awesome!" like 15 years ago...
Now it just makes me wonder "how long before someone uses it to hunt down their favorite target demographic for arrest/deportation/extermination" for a split second before I remember "if this is what we are seeing as the public, then someone is definitely already doing that"
Can't wait to see the wapo articles praising the musk drone defense network for flushing out the undesirables from [area] and only having a 20% false positive rate of elimination.