Cross-linguistic research demonstrates that phonologically conditioned allomorphy—where morpheme variants vary based on their phonological environment—is a widespread linguistic phenomenon found in many languages around the world.
The claim states that English is not the unique language where grammatical articles or morphemes vary based on phonological environment. Papers [4] and [8] provide direct cross-linguistic evidence of phonologically conditioned suppletive allomorphy in the world's languages, thus supporting the claim.