The claim you're making has been widely spread but is mistaken. /usr/bin/git is just a wrapper that execs the real git from /Applications/Xcode.app or /Library/Developer/CommandLineTools (depending on what you have installed), and some things will invoke the latter directly anyway; thus removing the wrapper is neither necessary nor sufficient to prevent exposure to the vulnerability.

I know; my point wasn't "`brew install git` and you're safe" - it was "Apple don't let you upgrade when you want, and even when they do let you, they don't give you latest."