The timing side vent does have a suction. I have noticed it while experimenting with the blocking/unblocking.
If the engine is running, and air is being expelled out the main breather hose by the piston action, then ANY open hole that connects anywhere to the crankcase is going to have a "suction". That doesn't mean it's needed.
As others have mentioned, it is merely a return line for excess oil expelled out the breather, that gets into the catch can. It's basically just a part of the pollution control requirements.
I can assure you that the Iron Barrel predecessor Bullets ran quite normally for 50 years without any of that nonsense on them.
Regarding any "filters" on the breather, the breathers are not intended to take any air in. They are intended to ONLY blow air out via the main breather hose which has a duckbill ONE-WAY valve on the end to PREVENT any air from coming back in.
Attempting to add an air inlet somewhere does nothing but circumvent the breathing system of the engine, and adds to unwanted pumping losses which lose horsepower.