Annular boosters on a Tunnel Ram

I'm not sure but the straw analogy might be over simplified for booster startup point measured in rpm.
To me, the straw analogy is about WOT. If pressures equalize, flow will stop. A large air bleed will lean out WOT due to the pressure it exposes because of its size. I do not believe this is the case when starting the booster though due to air speed and pressures a little throttle blade opening.