Most managers would have their reports' mobile numbers. Just start with the C-suite and work down. This is a case of hierarchy actually being an advantage...

In large corporations yes (For emergency procedures etc). Definitely, if most staff have a work phone (for email).

I think this means contacting them via email on their mobile phones.

I think is a matter of semantics, not of functionality. A smartphone is a computer per design, but no one is calling it like that.

My calculator's a computer, but I don't call it that. My game systems are all computers, but I don't call them that either (and never have, unless I was discussing semantics).

It may be, but it is not in hardware or software lated to the major "desktop" platforms. And they are by design far more locked down than your average laptop or desktop (just wish said locked state didn't leave the OEM so much in control).

A smartphone is not a computer any more than your electric toothbrush, which happens to have a CPU and Bluetooth for whatever reason, is a computer.

In this context "computer" means "desktop computer" or "laptop computer".

its a colloquialism

computer = desktop\laptop