that’s not the only reason that ambient air comes in. It’s mainly due to an “entrained gas” effect.
Similar to how orienting the ends of two straws at a 90 degree angle, then submerging the free end of one into liquid, while continuously blowing into the remaining end will create a negative pressure zone large enough to raise the water up the straw and then spray all over. This is a continuous stream of air. Not a pulse with a trailing low pressure zone.
This is the principle that an eductor pump operates on:
