Git not autocompleting with the switch command
Git for Windows does not ship with tab completion support for PowerShell. You had an outdated version of Posh-Git installed, a third-party package that provides tab completion for Git in PowerShell.
Much like the original completion support (developed with Git, for Bash, ZSH and tcsh), these need to be updated to support new/changed command line syntax, so make sure to update regularly.