I assume that when you say "main command" you just mean some other, normal, non ++ command. I think this will only be an issue if the duration of the pause in the non ++ command is longer than the pause in the ++ command.
It might help to understand that ALL actions (except for VC.Pause) must run on the main UI thread. Anything that happens between actions such as updating the history window must also be performed on the main UI thread, because it is interacting with the UI in order to show you stuff. So looking at the ++ command, the first action following the VC.Pause action will not be able to execute until any other commands that are hogging the UI thread are finished and release the thread so others can use it.
But as Nime5ter points out, it's not really an issue since you should not be using long pauses anyway, and if you do need them they should be put into a ++ command.