That's certainly true for the overwhelming majority of street operation, but at high-load or full-throttle operation when there's the combination of low/no vacuum and increased blowby, crankcase vapor will flow out of that intake side. Whether it's worth it to install a catch can on that side will depend on if you see evidence of anything other than a minor amount of oil in that tube or the intake tract after a stint of high-load or full-throttle operation.
there's a company that sells a 3 port can, the idea if plummed correctly, once the intake hits zero vacuum, the 3rd port is run to the intake duct pre throttle body, the air rushing by will create a vacuum to continue to pull crank case pressure thru the catch can and not just back out the clean side into the intake duct without the catch can.
there's also a clean air side, it replaces your oil cap with a mesh filled media to attract oil before the hose runs to the oem clean air spot in the duct.
but as you said, I don't believe my suv ever sees a non vac in the intake state, since it seems to be a tight engine blow by wise and it's not driven like a race car. I think I will be putting a 3 port on my ls3 car thou. Just been lazy.