In part this is due to how this still has a commonly accepted pressure ratio (vapor pressure at condenser:evaporator ought to be ~10:1 for fridge-like compresso

In part this is due to how this still has a commonly accepted pressure ratio (vapor pressure at condenser:evaporator ought to be ~10:1 for fridge-like compressor designs to be happy), and in part because having the propane equipment outdoors and only interacting with water/water-glycol-mix for thermally connecting to indoors makes the safety aspects far easier. It's now hard for propane to sneak indoors, form a mildly concentrated puddle, any blow up from static discharge at the next opportunity. Propane/air heat exchanger are normally dangerous due to difficulty of dealing with a leak even if you use a sensor to detect leakage of dangerous concentrations of propane into the air. At least if this is indoor air.