Not true. They blow air out two places.
1. Evaporator air: Out the front vent (cold air).
2. Condensor air: Out the hose that goes out the window. (hot air)

Air for both #1 and #2 come from the air in the room. But if #2 is
blowing air OUT of the room that means that:
a. The room will eventually be sucked dry of air or
b. Air is coming into the room from somewhere else.

Unless a magician is creating air in the room then it has to be drawn in
from some other room, cracks in the walls or ceiling or somewhere else.

The thing is obviously going to be less efficient than a system
that keeps inside air inside, but:

If a quantity of air Q1 comes into the room and is
separated into to other quantities, a hot, wet Q2, and
a cold, dry Q3, and Q2 is exhausted outside, then
the air inside Q4) will obviously be cooler and dryer
than Q1. (but warmer and wetter than Q3).

If you assume the worst-case, that Q1 mixes thoroughly
with Q4 before being sucked into the unit, then
you should *eventually* reach equilibrium at q4=(q1+q3)/2.
If you get the best case, where ALL Q1 goes through the
unit before mixing, then you reach equilibrium at q3.

--Goedjn