I haven't seen anything that shows they are 'Potted' or hardened. They could be, and it's not obvious or advertised?
That said, Garmin's lawyers disclaim any liability for damage when mounted to a firearm. So there's that, lawyer's. Then there is the Garmin EE who build it, who in deeds says he had one mounted to a firearm during development and reports no issues.
I don't think they've been fielded long enough - we don't have enough sample size or time to know if any meaningful issues will result.
Seems like for the most part it will be fine, but you risk loosing your 600 dollar chrono. Personally, I am mounting to my 22lr without Zero regard and will mount it to centerfires if the situation dictates it without much thought and we'll see what happens.