I am A-list and wife is companion. We almost always fly together.

I board in my position and she usually comes on in the B's.

I've yet to have an issue holding a seat. I sit my bag into her seat and tell people it's for my wife.

I think the issue of 'boarding together' is that your companions ticket does not indicate companion, so it's hard to police.

What's the big deal about just holding a seat?