Occam said:
I would question the lawfulness of a command that directs a member to provide their cellphone number, when a suitable landline number with voicemail is available.
CoC: Give me your cell number.
Bloggins: Here is my home number.
CoC: Is that what I asked for?
Bloggins: No, but it is good enough.
CoC: With your land line can I send a quick text during the work day/at lunch to you if I need you to do something or need to pass some information on when we aren't co-located?
Bloggins: No...
CoC: If there is a recall and we need you to return to the unit ASAP is it quicker to call your cell or wait for you to get home and check your messages?
Bloggins: Well, I will probably have my cell on me so...
CoC: If there is an disaster and landlines are affected but cell phones (whose towers contain generators and battery back up) are still working how should I try to contact you?
Bloggins: You should call my cell...
CoC: If we are meeting off base for PT and I get called away/stuck in traffic should I leave a message on your home phone, which you will not be able to check until after work or should I call your cell?
Bloggins: I guess you should call my cell...
CoC: Right, give me your cell number.
Why do I have to update ORLs when a vehicle's condition is tracked by DRIMIS? Why do I need to keep the parade state current when all the same information can be found in Monitor Mass? Why do we sweep and squeegee the vehicle bay every week, even if we have not used it during that time? Because the CoC said to.
We live in a connected world and your CoC expects to have your cell number. Does that mean they will be calling you all the time? No. Do you need to have your cell on/with you all the time? No. But you do need to provide your cell number when told by your CoC to do so.
To be quite frank, it doesn't matter if providing your home number instead is suitable. When ordered to do something you do it. Just because you think something is stupid to do does not mean you don't have to do it. Stupid orders are still lawful commands.