IF you run a vacuum line from the throttle to the breather tube and you are drawing air thru another breather, then yes, you are sucking in unmetered air thru the other breather into the intake.
Without another breather. There is no crossflow (like sucking out a Coke bottle, its a vacuum). So no unmetered air.
If you plug the throttle vacuum line, and just run 2 breathers "venting" to atmosphere, not fed into the intake, then no (sort'a). You did meter the air coming into the intake, and the blowby (.1%) was metered and now going to atmosphere.
I did the second with my S-trim install.
