I look at that as an inane marketing ploy, a ploy to sell more product.
I have a B&S 3400 psi pressure washer with an AR pump. The manual states:
Pump Oil
DO NOT attempt any oil maintenance on this pump. The
pump is pre-lubricated and sealed from the factory, requiring
no additional maintenance for the life of the pump.I can only laugh, 'for the life of the pump', as short as it might be.
My pump oil gets changed every spring. Yes it's not a pull the plug, drain and refill. There is no drain plug, in fact there is no way to even check the oil level, more silliness.
I put the washer through its paces to get the oil warmed up, remove the pump from the engine, remove the 'vent cap', drain, remount and refill with 4.5 oz. Mobil 1 10W40. The selected lube is based on conversations with and recommendations from AR's technical staff.
Anyone with half a brain knows that there is wear in any moving device and that wear relates to more wear with the abrasive materials that become suspended in the lubricant.
It's the easiest thing I can do to prolong the life of the pump. I try to help my bottom line, not B&S's or AR's.