Continuity Conundrum: DC Comics Presents #52

Here's a quandary for any self-appointed Continuity Kops out there:

Did DC Comics Presents #52 "really happen"?

The question springs to mind due to Ambush Bug's recent appearances alongside the Doom Patrol these past few months.  DCCP #52, you may remember, featured the Bug's less than glorious debut in a story teaming Superman with none other than the Doom Patrol.

"It was only ink...I think!"

Of course, this was not the current/original incarnation of the team as seen in the currently ongoing monthly series, but Paul Kupperberg's "New Doom Patrol" consisting of original member Robotman/Cliff Steele and new recruits Celsius, Tempest, and Negative Woman, all of whom most recently appeared as Black Lanterns in Doom Patrol #'s 4 and 5.  The story, entitled "Negative Woman Goes Berserk!", written by Kupperberg and drawn, and, I suspect, co-plotted, though he isn't credited as such, by Keith Giffen,  has Superman and the Doom Patrol dealing with the twin menaces of rogue Patrol member Negative Woman, who has, as the title suggests, gone berserk due to the effects of the negative radiation that gives her her powers, and new super-villain Ambush Bug.  
That's right, folks, I said "villain."  Early in the story, the Bug literally pops into the middle of a WGBS broadcast of the annual Metropolis Day Parade and kills the city's District Attorney.

Despite this bit of shared history, since Ambush Bug popped up on Oolong Island at the end of Doom Patrol #9 and started working with the Patrol, neither he nor Robotman has made any mention of the fact that they've ever met before.  Which leads me to ask if, in fact, they actually have.  Are the events of DCCP #52 still part of DC canon?
Complicating things is the matter of that murder.  The fact that the Bug apparently killed a man has, except for one panel in his second mini-series, never been mentioned again.  In subsequent appearances, beginning with his second one in DCCP #59, the Bug has been treated by Superman and the super-hero community at large as a mostly harmless trickster figure rather than an escaped murderer.  Yet, you'd think that someone like Superman wouldn't be the type to tolerate a killer running around his city pretending to be a super-hero, wouldn't you?
You could say that DCCP #52 got erased during the Crisis on Infinite Earths or any of the ensuing half dozen or so times that the universe has been destroyed and re-created from the Big Bang up in the last two decades, except that it seems to have been forgotten well before the Crisis.
In the end, of course, we really have to remind ourselves that it matters little.  As the Bug himself says of the incident in Son of Ambush Bug #6: "It was only ink...I think!"  Or, as Alan Moore gently reminds us at the beginning of "Whatever Happened to the Man of Tomorrow", all super-hero stories are imaginary, after all. Writers are free to ignore or acknowledge past stories as it suits their current purposes, and all that really matters is telling a good story.  Keith Giffen has certainly been doing that in recent issues of Doom Patrol.
Thus, the real reason to ignore "Negative Woman Goes Berserk!" is because, despite its "historical importance" as Ambush Bug's first appearance, its otherwise a pretty lame and forgettable issue.  However, it does have nice art by Giffen, who was still drawing in a somewhat more realistic style than he'd use for later Ambush Bug projects.