From the NEWS section in the page: Improvements grep -i in a multibyte locale is now typically 10 times faster for patterns that do not contain \ or [.

From the NEWS section in the page: Improvements grep -i in a multibyte locale is now typically 10 times faster for patterns that do not contain \ or [. grep (without -i) in a multibyte locale is now up to 7 times faster when processing many matched lines.