This is my opinion. I can't cite anything. I normally think 99% of the time people over think these counts unless you are close the line where you move from not needing an audit to an audit. I would actually amend for the reason you stated in this case.
I would add with the software our firm uses it is simple and not very time consuming. The hardest part would be someone has to call the client and apologize for the mistake. I would rather do that than have a discussion why an IRS letter or agent shows up asking about the number. In short the cost of amending seems low and the bad thing of not amending seems high even if you don't know the chances of it happening. In fact your firm may have spent more man hours (minutes most likely) debating to amend or not than how long it would take to do the change on the software.
That is my 2 cents.