Arguably, but what if the company wants to find proof of, say, two employees colluding to exfiltrate sensitive data or something like that? Would they have to convince them to turn in the PGP signed logs?
More generally like the parent I don't see why a company couldn't have full control over their corporate tools.
> two employees colluding to exfiltrate sensitive data or something like that
In that case spying Slack usage is simply not enough: the employer should need to spy every single move every employee makes inside and outside the company, which of course it's not possible (well, except if the company is located in a fascist state).
What if those two employees collude to do something like that via their own private phones? Should employers have access to those too?
It doesn't seem to me like any of this really does anything, since there are (and should be) plenty of ways that employees can communicate without their employer having access.
More generally like the parent I don't see why a company couldn't have full control over their corporate tools.