Re: "in practice this one is no big deal."
Correct me if I am wrong in this but as far as I understand, airplanes are very safe because all the flight control software is written independently from specs in triplicate. Then all 3 control programs run concurrently with a majority poll deciding what happens if one program is in disagreement with the rest. So, in theory and pretty much in practice, you can ride out any one bug.
But... this was not on the flight control software, so there would have been no triple redundancy around. Granted, the likelihood is pretty low of this flaw coming into play, but you still have a critical component that is not triple redundant so finding such a flaw is scarier than flight control software proper, isn't it?
The fact that it wasn't likely to be a problem in this particular instance is not a reassurance to the QA and redundancy factors for secondary but critical programs.
On the other hand, the fact that they did find the bug during lab testing is a good sign.