My take on these affects of decarbonization is that there are two ways you BURN oil: one is you leak it by the valve guides and it burns in either in combustion chamber or the exhaust. The other way has two corollaries and are due to rings.
The first corollary says the rings are not sweeping the lube oil from the cyclinder wall and it gets burned in the combustion chamber. The second also comes from the carboning of rings and that is the instance of large blow-by due to carbon stuck rings. The large blow-by causes such velocity backwards in the PCV system that oil is carried into the intake and thus the cylinder.
We have had numerous cars in the last few years with either huge smoking problems or no start due to lack of compression, fixed by decarbonizing. Had a 600SEL from a board (mercedesshop) member tow his car over 100 miles after the diagnosis was no compression. I talked to him recently, over a year later, and the car is doing OK.
We poured a small amount into each cylinder through the spark plug hole and rotated the engine by hand a number of times and then let it sit for a few hours. After running and getting warmer up we do another car through the plenum and wait 20min or more and drive it hard.
Bosch Master, ASE Master, L1
33 years MB technician