You’ve measured the difference?
All you need is enough pressure to fill the float bowl. Which isn’t a problem with the vent sealed.
Even David Klaus has this listed as a solution to the topic of overflow from the vent.
IDK what else is needed to conclude this is a non-issue. Run adequate valve cover venting, seal the fuel pump vent, and save yourself the cleanup.
A strong suggestion to help reduce any mist from exiting your fuel pump vent:
If you find yourself with an issue, clean the oil from your pump vent and using
either nail polish or silicone put a ‘dab’ on the screen itself. This ‘dap’ can
completely cover the brass vent screen without negatively impacting the
function or life of the pump. This will naturally act as a restriction to the
amount of air allowed to pass through. That will lower the velocity of the air
passing through and its ability to carry oil mist with it.