I always figured Boba had been briefed on the situation and it was a warning shot of sorts.

There's an interesting dynamic between Vader and Fett - who else could've criticised Vader "he's no good to me dead" etc, it's like the two guys definitely understood each other even when at odds, with mutual respect.

That's why I found Boba's movie demise disappointing on subsequent viewing (though a cheap laugh at the time) and surprised Anakin and Boba didn't have any kind of relationship to speak of in the prequels, despite every other character knowing every other character (Yoda and Chewie ..really?!)