I argued with the Box Stores supplier endlessly, for the very reasons you mentioned. But they went for the buck anyway. They have hundreds of "returns" now. The underpowered model they sell, is part of the problem.
Picture the enthusiastic homeowner with no trade or mechanical skills, re-doing his/her plumbing, gas lines, and double-wall flue. Then it doesn't work, or it does, but not the way the eager salesperson promised it would.
If someone other than a professional installs what I sell, a binding disclaimer goes with it. I disown the warranty, and the factory handles it.
Must go check my 3 ton AC, pulling 15.3 amps but not cooling. 83 F & muggy, oh well.