Best answer by melvimbe
You can setup an alexa group with your echo dot so that music/streaming audio commands play the audio on your preferred speaker. the playbar. You cannot have Alexa (echo dot) speaks through your playbar. (You could with a fire tv and TV, or with various adapters that come with other issues, but I don't think that's what you were getting at).
I can't say that you were or were not mislead, since I do not know where you got your information from, or what assumptions you made based off that information.