Seems like using a flag that gives an unknown contact your home address is a bad idea. That information might not be something we want to communicate right off the bat.
Since we are constantly broadcasting at high energy and with interesting patterns, I wouldn't worry about that. Everyone who sees this flag is either from Earth or knows its position very well.
I just read that and the Dark Forrest and that (fundamental) part of the book honestly made no sense to me. His claim that you can't locate a signal's source location was in complete conflict with everything I thought I knew about astronomy and how we locate things in space.
One suggested solution to the Fermi paradox is that any civilization that gets noisy enough to get noticed quickly gets attacked and destroyed (or taught to hide better in the future...)