Pocket mode bug
After calling my new Asus Zenfone 8 the worst phone ever for more than a month due to pocket mode issues, I finally found what's causing it.
It's not all of the answers here: https://zentalk.asus.com/en/discussion/55617/pocket-mode-doesnt-work
The real issue is a setting of the Google Assistent allowing it to be active in lock mode. Once I switched off this setting, I finally stopped calling everyone while being on the bike, sending text messages when being in the pub, etc.
No clue why this setting is enabled by default, but I suggest everyone to disable it.