I think it’s the harsh consonant sounds. I’m not a linguist and am sure there’s some term for it, but it seems like we identify words in English more from the distinct “framing” of the consonants and are more flexible about hearing variations in how the vowel sounds in between are pronounced.

Like, it’s the same reason that whispering (which largely takes out tone/pitch of vowel sounds) is super easy in English, but more difficult in some other languages.