Modern navigation equipment is so accurate that reciprocal aircraft on the same airway at the same level would probably collide. I’m used to watching traffic on the same airway, opposite direction, 1000’ above pass directly overhead without even being a wingspan off track laterally, the fuselages line up exactly.
Then a minute or so later you hit the wake turbulence and if you’re below same direction traffic you need to request an offset as you stay in it due to both aircraft tracking the airway so precisely.
Often ATC will instruct aircraft to offset as they are too close together to make out on the radar screen.