I'll third this^^^^^^.
I don't have a fuelly bike but I have a direct injection turbo car engine.
There is a lot of evidence that under some conditions, even with a catcher, some fine particulates from the crankcase get through through the filter to the intake.
In direct injection cars the particulates and oil vapor hit hot intake valves and create carbon.
Because no fuel is going past the intake valves in direct injection or in butterflies or carbs of a Ural, there is no cleaning by the fuel and it's additives.
The fix in DI cars? Dealerships charge for very expensive intake cleanings to remove the carbon.
Not sure why there is buildup in a throttle body but not in carb bikes, it should be cool so it isn't cooking anything.
Maybe the oil/carbon mix is ideal for agglomerating to create build up.
It could be that the throttle body creates the perfect set of conditions of air flow/stalling that allows build-up where a carb doesn't.
I have always vented the crankcase to the airbox in my carb bike, no issues and never see any buildup in the carb bodies.
I'm against venting to the environment, as it is really a bad idea. There is enough fuel and oil that makes its way into waterways.
I'd look for any causes of excess blowback in the engine itself, put in an inline catcher and still vent to the box.
See if that helps.