A friend interprets each delay as rejection and asks for explanations about the last-seen time.
I propose to discuss realistic expectations before each message becomes a bond verification. In the example, it is made clear that work, school, and rest can interrupt the response.
Digital presence does not amount to complete availability. Establishing a boundary does not authorize deliberate coldness; it allows to distinguish an important communication from a request for reassurance that the phone, alone, cannot solve.