The retcon hinges on Degesu (Shin's brother) stating that killing people is outright black magic, when Gomah theorizes to use Shenron to get rid of the Z Fighters, and this is even without mentioning anything about power levels. Degesu states that Shenron is powered by white magic, for Dende is a good individual, so he should not be able to grant an evil wish.
Back then, in the manga, it was assumed Shenron could do it, but now not anymore.
In my perspective I want to try and balance out the two standpoints, but I also recognize that a retcon is a retcon.
So, going by people and staff's votes, Shenron will lose Death Manipulation and the current justification is going into the weaknesses section, as something he isn't able to do, even though he was formerly stated to.