Almost! Here's the stupid problem: the dictate text feature requires that you decide ahead of time what language you are going to dictate in. I'm also pretty sure that you can't toggle the languages on the fly when using CarPlay – I think you have to actually change the language setting on the keyboard.
The "transcribe text" feature handles the dynamic language, identification, and mix of languages perfectly… But does not have any hands-free way of stopping itself when you stop talking.
So one feature handles the starting and stopping well, but can't handle the language mix. The other handles, the language mix, but not the starting and stopping.