no offence to air conditioning engineers but you can teach joe bloggs in a day how to install a split type air conditioner and to understand how it operates,
Why do you think that AC engineers only fit splits?

We air condition 2000 seat bingo halls to achieve 21C at table top height - you can't do this with splits. What about air change rates? smoke extraction? these all have an effect on load. What about the 2000 seat club being only part full? this also has an effect on load.

There is much more to air conditioning than fitting splits