I spoke with experience of repairing cars in Pakistan and not the USA. The throttle cleanup is merely a gimmick coined by local roadside mechanics in Pakistan who are used to "carburettor ki safaai" from the 1930s.
Have you ever wondered why your idle control on old style cable throttle goes a bit crazy after a few "services" - the reason is that the idle control motor is cleaned with quick flash solvents which removes all oil that is soaked into the bearing surfaces of the motor - its like zeolite bushing - its impregnated with spindle oil.
If you read service manual even specified for driving in 3rd world countries or in the bush/desert etc, the only time they actually recommend to clean the throttle is when it starts to jam the blade (modern ECUs will throw a fault for it too - which I have never seen one throw till yet)
carburettor cleaner itself will not hurt the cat converter or even coat the plugs, You may have heard of catch cans etc for PCV and its not a good idea to plumb it back into the intake manifold - cars in the early 1900s had a fume tube under the car which pushed out crankcase gases as it went down the road (just like a honda CD70 engine) - nearly all cars built after the 1950s have had some sort of PCV system employed to burn off that oil vapor - its such low in quantity that I dont think a driver will ever experience the loss of performance from an econobox production line engine being used on public roadways.
This PCV system is kind of like a self cleaning system for oil - along with oil vapor it also sucks out moisture too which kills oil pretty quickly.