Godot 3.x and 4.x are major release versions that break API compatibility. It is very unlikely that you are developing a game for both versions the same time, so no need for a tool to switch easily between them.
I am not talking about general stability, but API stability. Normally you want a game project to work with any version of the Godot 4.x release cycle.
You don't need such a tool to manage version if the engine has a stable api on major versions. And you certainly don't want to jiggle with multiple versions when developing a game, or be stuck on a specific minor version because the engine broke API compatibility outside of major versions.
if your game is in production you risk introducing bugs with every update, but you will probably want the latest version of the engine for your new game