This isn't so much of an advantage for "bar" and "baz". Those sound pretty distinct to Americans, now, but "r" -> "z" is a known type of sound change, which implies that for some people they'll sound the same. "R" -> "s" is attested in Latin, presumably because "z" wasn't an option. (Latin fricatives don't have voicing distinctions.)

For an only slightly different current example, the second consonants in "virile" and "vision" are perceived as distinct in American English, but identical in Mandarin Chinese, which is why the sound is spelled as "r" in Hanyu Pinyin and as "j" in Wade-Giles.