From the Help
 
Code:

Selling Kits
If the order includes a type K Selling Kit, you can release a partial quantity 
on a  parent product without having to individually release all its components.  
When you release a partial quantity, you are asked if you want to change all 
the components proportionately.  If you indicate yes, all the component 
quantities will be changed in succession in direct proportion to the change 
made to the parent product. 

 
Do you know how the question was answered?

We have a lot of type K items. In fact a huge majority of them, so we are pretty familiar with the workings. We've been using DBA since 2000 (I think we started testing and setup with v98.x) and B/Os in SO-E (or changes to quantities in SO-A) have always worked the same - it asks you if you want to change the components proportionally.
 
That isn't to say that for some reason it didn't that one time, but the more likely explanation is that the person releasing it just didn't notice the pop-up...