A lawnmower is 4 stroke, this is true with 2 stroke but there should be no oil on the walls above the rings on a 4 stroke.
Wait a minute...
VW bugs are air cooled 4 (FOUR) stroke engines. In really cold weather automatic chokes would not turn off and thus the engine was fed a rich mixture, not unlike overspraying fluid into the intake as in the example we are discussing.
In these conditions it was not unusual to find after driving as short a distance as 15 miles that when then checking the dipstick you'd find the crankcase seriously overfull of your oil as diluted with gasoline.
This if not corrected by EXTREMELY FREQUENT oil changes or not driving till temps went up caused what was called "winter kill" of the engine. Basically the engine would be ruined due to lack of lubrication because of washing the oil off the moving parts thus permitting metal to metal contact AND, of course, the contaminated oil didn't treat any of the bearings very kindly.
Can you spray lots of stuff into intake and get away with it? Yes of course you can but you may be causing extreme wear to moving parts through unlubricated metal to metal contact which is NOT A GOOD IDEA.
Do I ever use starting fluid? Yes, sparingly, not to keep an engine running for a period of time just to get it to start. To partially avoid the risks involved I often use WD-40 in place of starting fluid or carb/choke cleaner and find it especially effective with chain saws and other small engines.
I'm not the starting fluid police but I have observed the down side of its over use when stationed at Minot AFB 15 miles north of Minot, ND where my personal low temp I was out in was 47F below zero and I experienced temps more than -40 every winter.
In my example the cold weather caused the choke to stay on feeding a rich mixture for an extended period of time. The cold was not otherwise needed to cause problems. The problems were due to the rich mixture diluting the oil and washing down the cylinder walls, rings,and pistons. Just because the engine doesn't instantly seize up when keeping it stunning with a spray can does not imply it is a safe practice as regards the engine's longevity.
Pat