FWIW, that had been claimed - read the link. I read about these facts in other publications, so there is something to the facts (but perhaps not to their interpretation.)
But as I understand the drilling at the Kola Superdeep was stopped in part because the funding dried up and in part because every additional foot was immensely expensive. It took something like a week to pull the string out to service the tool, and another week to lower it back... Basically the depth that was reached was at the limit of our current drilling technologies. Perhaps with the latest improvements another mile can be made. But it's 4,000 miles to the center of Earth; they can't be traversed without an autonomous machine that is protected by force fields (not with a material, short of Unobtainium;) it had been proposed many times in science fiction.