The function appears to work correctly for all inputs I've tested so far. However, I noticed that for words with more than 6 letters, the function only extracts the last 4 letters and converts them to uppercase, while the remaining letters are left untouched. For example, "The Grapes of Wrath" becomes "WRATH", "The Barber of Seville" becomes "SEVILLE", and so on.

Please feel free to test more inputs and update me with any additional observations or questions you may have!