Given Americans' general indifference to perfect grammer, if it "sounds" right they usually don't make a fuss. So they might have learned something new as well.
As a result, U.S. troops began asking other soldiers questions that they felt only Americans would know the answers to in order to flush out the German infiltrators, which included naming state capitals, sports and trivia questions related to the U.S., etc. This practice resulted in Brigadier General Bruce C. Clarke being held at gunpoint for some time after he incorrectly said the Chicago Cubs were in the American League[7][8][9][10] and a captain spending a week in detention after he was caught wearing German boots. General Omar Bradley was repeatedly stopped in his staff car by checkpoint guards who seemed to enjoy asking him such questions. The Skorzeny commando paranoia also contributed to numerous instances of mistaken identity. All over the Ardennes, U.S. soldiers attempted to persuade suspicious U.S. military policemen that they were genuine GIs.
This is how it actually works. The brain machine learns from available data and sorts out which is correct. "Sounds right" is the output from that neural network. The "rules" are then derived from what some set of people think sounds right.