I just went to the interfax link in your article, got the url, punched it into google search, then the "translate" part of the first link that showed up.
The "source" is not named in the entire article. He is simply described as "source familiar with the situation". The opinions that follow are his. He also notes, correctly, that if this legitimacy business goes too far, then the legitimacy of the USSR and other states is questionable as well.
But the issue here is not the quality of the General Prosecutor's decision, but the fact that the review is taking place, alongside with the decision that the transfer of Crimea in 1954 was illegitimate, and we know what happened to Crimea.