If you used the pump to pump antifreeze into the system, then it would have gone into all the cold water lines.
They sell a plug you can put on the city water connection, and use a compressor to force all the water out of the system when all the taps are open.
Not sure why they told you it wouldn't get antifreeze in the outside hose wash.
There could be an issue if an owner accidently used the outside hose and forgot about the antifreeze being in there.
Glad I don't have to winterize here!