Source being? I can write right now that they competed for a burrito.
In fact this seems to be a bad edit as shown here:
14:16, March 30, 2013 Reinhart77 (wall | contribs) . . (8,426 bytes) (-9,573) . . (Reverting to an earlier version before Forbidden Library content was added)
When Reinhart77 reverted the article, some fanon come back with it. This "official" backstory wasnt there before this and searching in Google about this doesnt return any relevant results. This doesnt appears in manuals too and IMO doesnt even make sense.
Nagumo deleted this fake info (Revision as of 18:59, October 30, 2012 with the username "Nagumo baby") but the revert undid this clean up.