Basically it makes a sorted list of all the ancestors of the 1st profile, and the 2nd, and then compares the two lists looking for common ancestors.
So I suppose, having made itself a list of all the ancestors of the 1st profile, it could then compare that with any other list it's got handy, eg a surname search list or a category.
This would tell you whether anybody on the list is a direct ancestor of your target profile.
This has potential. For instance, at present, if you want to know if you're descended from a Mayflower passenger, or a Duke of Normandy, or a Magna Carta baron, you can start trawling your tree, but you don't know which direction to go, and most directions will be dead ends, and you get lost in all the backtracking. The Quick Links help, but you have to go through the list.
If you could just compare your complete ancestor list with the Normandie surname list or the relevant category, you'd have the answer.
So long as people don't try it with all the Unknowns or Unsourced profiles. Which they will.