Comment # 17 on bug 1163592 from Martin Pluskal

(In reply to Michal Suchanek from comment #16)
> I am not going to reverse-engineer rpm to figure out why it sets %group to
> %group to fix a cosmetic issue which is easily avoidable by setting the
> optional group field for KMPs, sorry.
> 
> I could tell you that I put it on the bottom of my TODO list but that means
> it will never get fixed.
You could have tried running "rpm -qi" instead to find out there is actually no
problem to solve - apart from updating system original reporter is using ...

But as this is on bottom of your TODO I guess you will never find out.