That's not how such an algorithmic association would work. It's not that poorly made that searching the two together lists him alongside other presidents as a president; this information about presidents is likely derived from a third party source (often wikipedia).

That said, there ARE times in which their third-party sources are messed with which WILL botch the results. That may be the case here, but it does not appear to be the case.

Edit: it appears it was indeed what I suggested it may be; Google had been sourcing presidential information from wikipedia, which had been edited to list him as a president.

This is not an algorithmic issue in any way shape or form, just simple code.