Yes, if throttle body/IAC passage is getting an oil coating then there is a problem with PCV system, even over a long time.
First the oil vapor itself only comes from the Blow-by, the hot gases from combustion, blow-by vaporizes some of the oil on the lower rings, piston sides and cylinder walls as it escapes into the crank case area
Bearings and valve train can't vaporize oil, unless there is a major engine failure,
, they do not get hot enough to vaporize oil.
Cheaper oil causes more blow-by oil vapor, just FYI.
PCV system is there to create a slight negative pressure in the sealed engine, crankcase valve cover areas.
The breather/vent hose is there to allow fresh cooler air to be pulled in to help condense some of the oil vapor.
No oil vapor should be flowing out of Breather/Vent hose unless there is a problem with the system, so throttle body should not get coated with oil, ever.
Over time blow-by will increase as rings wear down, high miles, so the amount of oil vapor will increase, this is why Catch Cans were used, but between PCV Valve and intake, not Vent
And you could also change to a different PCV Valve, increase negative flow in the engine to compensate for more blow-by.
All gas engines operate with approx. 18" of vacuum at idle, 4cyl or V12, but blow-by is higher as cylinder numbers increase.
PCV Valves adjust flow by vacuum but allow for more flow on a V8 vs a V6 or 4cyl
So if you have an older V6 you may want to use a V8 PCV Valve, they are often a common size
Common old school test for PCV system was to have engine warmed up and idling then pull out dip stick, there should be a slight negative air flow down dip stick tube, it should be sucking in air.
You can use small piece of paper towel or toilet paper sheet placed on tube, it should be sucked to the tube, not pushed away.
If there is an out flow if air from tube then PCV system is not working as it should, and yes Blow-by could be going out Vent hose causing oil coating on the throttle body.
If engine is not sealed well enough then at higher RPMs, higher blow-by, the Vent hose can become an out flow point, because air is being pulled in from other places.
The PCV Valve is setup to maintain the negative pressure thru out the RPM band, thats what the weight inside is for, it adjusts the vacuum level in the crankcase/valve covers
The catch-can is added because of higher oil vapor levels, it is not uncommon for PCV Valve system to include a fiber filter with the valve on 4cyl engines, and on the under side of valve cover on V engines, this allows oil vapor to condense from air stream before being pulled into the intake, which is what a catch-can does, cooling the oil vapor out of the air stream