Relevant that those four words still make sense if we change the only vowel with the other vowels? Like big, bag, beg, bog, bug? Not just relevant...
All four of the words in that sentence still form common English words if you change the vowel to any other vowel. There may be other words that work, but I don't know them. ("Rim," which was suggested earlier in the puzzle, technically also works, but I didn't know "rem" and "rom" were considered words until I checked, so I wouldn't consider that "common.")
Nice job everyone, particularly Acridian for the solve.