I assume you are aware that they don't put the aircon in? Pre-install simply means that they put the pipework/feeds in place.
When I completed in July last year I was stunned that the words 'pre-installed airconditioning' didn't mean they put the units in. They have since changed the wording to 'airconditioning pre-installation' which makes it read differently - although you would be forgiven for assuming it did mean that the units were put in by PW. That was €1,600 I hadn't budgeted for gone!!!! Owch.