Those were my thoughts too. However, if the user picked an extremely common word, with common letters (which makes it a common word), then shaving off 50% each time is more helpful than eliminating the 10% that don't have the recommended, most common letter.
Of course this is all theoretical and should be tested before changes are made (which I failed to do initially).
I don't mind occasionally having to reinvent a wheel; I don't even mind using someone's reinvented wheel occasionally. But it helps a lot if it is symmetric, contains no fewer than ten sides, and has the axle centered. I do tire of trapezoidal wheels with offset axles. --Joseph Newcomer