Come back after several hours or even a day and pull the parts, rinse and blow dry or just wipe them down with some Corrosion X. Assemble the parts and you have what looks like a brand new engine.
With fuel or methanol you just pour some in, wait, flip the engine. A lot simpler and no worry about discoloring the finish.
There is no scrubbing, rubbing, or working of the parts to get them free or clean. They just wipe clean
If you are referring to the congealed castor then the same is true for methanol. If you are talking about varnish then this is not true of either. But when I used antifreeze it took less effort for the varnish. But again a lot more trouble just to free up an otherwise clean engine.