The great swindle that capitalist ideology has pulled is simultaneously convincing workers that 1) they are completely dispensable ('we can replace you'), but 2) that they are also completely indispensable ('we need you'). The former keeps the worker scared that they can be fired at any second, the latter makes the worker feel guilty about quiting (or not answering their phone at 6am on a Sunday).

The amazing thing is that, depending on what the corporation needs, the worker is made to feel either of these things.

The post in the OP is the worker feeling the latter, with a twist: being made to feel indispensable to shove off as much work as possible on the worker.