Is that your personal definition?
No, it's pretty much the most widely accepted definition, and has been for years.
See, there are various classifications, such as "damaged", "possible", and "probable". You don't get actual credit for those, you get those classifications. A confirmed victory isn't added to your record, and you don't paint it on your plane, either. Well, at least you don't if you're truly honest.
Of course, you can make all the claims you so desire. I'm sure you will.
I suppose the Russian hot shot can be forgiven for his mistaken claim. After all, since the planes he was accustomed to flying would not withstand the damage he felt he inflicted on the F-86, he probably figured he'd scored a victory. He probably also figured that since he wasn't good enough to fly a cripple home, his opponent wasn't either. Besides, he was too busy trying to save his own hide to see whether or not his enemy crashed, so all he had was an assumption.
Then again, he obviously felt he needed to finish that F-86, but wasn't able to because he was too busy trying to keep his hide intact, so maybe he did know he didn't score a verified victory, but decided to claim it anyway.