I don’t know what kind of business you run but I would imagine your customers appreciate the quality they receive from your establishment. Even if a parcooked burger doesn’t taste differently, the perception isn’t good.
I pride myself on the quality I serve and I would imagine that most people here do as well. We are posting and reading about food in our free time.
My kitchen is open and people are 3 feet from my grill and broiler, I know the reaction I would get from my customers if they saw me pull a burger out of the water.
For my business, shortcuts go against the very thing I hate about “fastfood”
Not trying to judge, just my 2cents