No, that has nothing to do with race. They have been doing that for as long as I can remember. It's CYA against predatory lawyers.
“What do the media style and dogma guides actually say? If you think the victim/perpetrator might be black, you MUST use ‘alleged’?”
There is an AP stylebook rule that says, as I recall:
Racial identification should not be included in any story unless such reference is clearly relevant to the story or when part of a detailed description of a fugitive.
http://gunwatch.blogspot.com/2014/10/are-black-people-carrying-guns-puplic.html