I am attaching a video recording, during this recorded test the piglin does not care about opening chests however did get mad when I broke a chest, all out of line of sight
Yes I tried in both Survival mode and Hardcore mode and got the same result.
Edit: I've run a slightly more thorough test (just tried it in a bastion remnant instead of just open nether) Still no difference if they do not see me they will not attack, and can confirm that I am on 1.16 pre-release 3/snapshot
After rereading the pre3 changes I have determined I am just stupid and thought i read that they will get mad if they hear you open a chest however it was only breaking desired blocks not opening them, however that would be a welcome change to make it harder to steal from them.