alibi does seem to get some use where it doesn't have the main meaning.
It seems to be related to having a shell stuck in the barrel of a gun, which is something one ought to tell someone about or at least make it known.
That can easily be metaphorised into just Does anyone want to mention anything important.
It sort of reminds me a little of a parting shot: something you say just before you leave.
So if we assume that the above is acceptable, is there a relation to the more common meaning of alibi (which means elsewhere, which is why the 'defence of alibi' means 'Couldn't possibly have been me, I was elsewhere at the time')?
A misfired bullet could be classed as being elsewhere from where it ought to be - the other end of the range - so the bullet is alibi.
At the end of meeting, all concerns should be 'on the table' for all to see and discuss. Those concerns that people have not brought up are elsewhere (in their head or in their notes) and if they are elsewhere then they are also alibi.
So, if my reasoning is even close to correct, the use of alibi in both a jammed weapon and points made at the end of a meeting means exactly what alibi is defined as - elsewhere
Which brings me to the conclusion that this use of alibi is NOT different from the original alibi.
From MetroPistol.org's FAQ (http://metropistol.org/FAQ.html)
An alibi or refire
At some point in the match your gun may jam or fail to tire. If this occurs during slow fire you’ve probably got enough time to fix it. If the gun jams during timed or rapid fire you won’t have enough time to fix it and finish shooting. When the guns jams during timed or rapid fire, raise your hand (the hand not holding the gun). Do not touch or attempt to clear the jammed round. If you do, the alibi will not be allowed. Rest the gun on the bench but retain your grasp on it. After the round the caller will ask ‘are there any alibis?” and see your raised hand (if not, yell!). (continues)
On a blog from 2009 the use of alibi is mentioned - oddly it ends with a similar thought that parting shot sounds about right.
From 'Iggy's bloog' (https://igelianphilosophy.wordpress.com/2009/09/)
My newest armyism is the military (tactical?) use of the word “alibi”. The other week I went to 2 command type meetings to represent the Red Cross. They were interesting mainly because I don’t go to them every week. Anyhoo, at the end of both meetings the person in charge would ask, “Any alibis?” I was wondering why they were asking if anyone had any lame-ass excuses at the end of the meeting. It didn’t totally make sense. Maybe there was stuff people were supposed to do but didn’t? It just seemed a weird way to end a meeting. Later I asked my co-worker about it. She told me when you go to the shooting range everyone is firing and stuff and then whoever’s in charge yells for everyone to cease fire. Next the person in charge asks if anyone has any alibis – meaning any more rounds in their weapon that they have not shot yet. So alibis are last bullets shot on the weapons range. By association, I guess, in the meeting world, alibis are the parting shots or last things to mention. No one had any at the meetings I went to – which was fine by me.
There is also mention of it in comments under the Merriam-Webster definition for alibi
Joe Venezia · Boston University
@Vera Croce, yes. At the conclusion of a military meeting, the highest ranking officer asks, 'any alibis'? This allows anybody in the meeting to speak their concerns.
Reply · Like · Follow Post · August 14, 2014 at 2:53pm
Vera Croce · Euclid High School
in the military, when there is a round-table discussion, and your turn has passed, yet, there is something to be added to your part of the discussion. "I have an alibi" is used to ask for time to add the comment. Have you heard of that before.?
Jim Skibo · SVP, Business Development at Exchange
At the end of our meetings, the question "Are there any alibis?" if often asked. I have presumed this means any follow-on or final comments, but I had never seen the derivation of that usage until Travis Hubble's comment below. Since I work in a quasi-military environment, this makes sense. For the non-military in the room, this term is alien but no one has ever explained it.
Travis A Hubble · Westerville, Ohio
In the U.S. military the term "alibi" is used in a briefing after everyone has had a chance to speak and the speaker or moderator, before closing, asks if there are any alibis, i.e. if anyone has any last comment that they may have failed to bring up earlier for whatever reason. This likely derives from an alibi shot which is an extra shot on a firing range one may be allowed to fire due to one's rifle malfunctioning during the regular round of firing.