I'm with you about following the manufacturer's instructions. Singer recommended kerosene to clean the inside of their machines, so that's what I use. I had forgotten that Elna recommended kerosene for their hook/bobbin assemblies. A point of interest is that the Grasshopper used a nylon (I believe it was nylon but it was certainly some type of plastic) hook pinion gear. So obviously Elna was not concerned that kerosene would damage the gear. And those gears have lasted from the mid-1940's until today.
I have no doubt that technological progress has resulted in more advanced lubricants and cleaning solutions than was available in the past, but that said, one of my Singers is a year or two shy of 100 years old, another is over 60 years old and the list goes on. All of them work like new machines. I also have a 55 year old Elna that works like new. I'm happy with using kerosene to clean and sewing machine oil to lubricate the gears and petroleum jelly in the motors.
One thing I'm absolutely certain of and that is using sewing machine oil to clean internal mechanisms is wrong. It will just attract lint and dirt which will gum up the works or even worse, allow abrasive grit to stick to moving parts.