The use of ⟨ŗ⟩ has it that gen.sing. "plague" "mēŗa" would be distinguishable from gen.sing. "measure" "mēra" and "bēŗu" would not show umlaut being pronounced with a close like the rest of its paradigm. Further, besides the 5th declension plurale tantum noun "bēres" ("funeral") another word that would have stem final consonant shift can be introduced - 2nd declension "bēris" ("a bay horse") both their gen.pl. will be bēŗu if ⟨ŗ⟩ is used. One could argue that the appearance of umlaut in gen.pl. "funeral" now allows to distinguish it from gen.pl. "bay horse" (assuming the latter is not subjected to umlaut), however, the more common occurrence of the words "I poured (a granular substance)" and "of funeral" becoming perfect homophones is likely to be seen as a net-loss by proponents of ‹ŗ›.