It really should be the default shell by now. I don't the see the point in Apple maintaining the 2007 version of bash with security updates when they can just promote ZSH which has near 0 breaking changes from bash
The former is nonsense, and the latter sheer unsupported guesswork.
The actual evidence from history of changing shells, from the Ubuntu and Debian worlds where they actually did make a change of shells (from Bourne Again to Debian Almquist) a few years ago, is that it doesn't drive people away in the first place, let alone away to Windows.
Even if one did a survey to make the latter not unsupported guesswork, one would have (if my experience of StackExchange is anything to go by) to account for all of those who answered that "My shell is Terminal.app." or "I have oh-my-zsh as my terminal.".
