Berachot 18 - aninut #2

How do the tanna and Rabban Shimon Ben Gamliel disagree? What is aninut? Bereshit 35:18וַיְהִ֞י בְּצֵ֤את נַפְשָׁהּ֙ כִּ֣י מֵ֔תָה וַתִּקְרָ֥א שְׁמ֖וֹ בֶּן־אוֹנִ֑י וְאָבִ֖יו קָֽרָא־ל֥וֹ בִנְיָמִֽין׃ But as she breathed her last—for she was dying—she named...