starting bitbake takes a bit and is useless for the help printout. This is minor, though annoying if you do it a few times in a row :/
I'm not sure we can do much about this. devtool supports extension through layers added to BBLAYERS and needs bitbake to tell it the final value of that variable - and that is needed for plugins to be able to register themselves and add arguments that are used to construct the help output.
Paul's comment makes sense. Additionally, keeping bitbake server alive would alleviate the delay anyway.