Great HVAC advice

Last week at an inspection, I had my buyer and a HVAC technician present. My buyer was asking the tech questions. One of the questions was: how big is the air conditioner and is it big enough for this house? The tech responded with the unit is four tons and gave the tried and true rule: 1 ton = 400 sqft of cooling. The tech asked how big the house was and the buyer said " about 1600 sqft, the tech responded with, its big enough! The house was built in the 50’s with additions… The buyer asked the tech about service, the tech told him to clean the condenser coils with a hose, while the system is running, stating that the system is designed to run in the rain. The tech gave a basic explanation of the refrigeration process and then he gives that kind of device?