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The crankcase is under positive pressure relative to the intake pressure... (it's only negative relative to ambient because of the vacuum caused by the intake) Unless you are saying that is an air pump somewhere that I I don't know of.

I am not saying that if you vent to air you will blow up the engine... The people that designed the engine had to design it to reduce the probably of failure so that you you get a failure after N million manufactured hours. If you are are going to say what is "best" for the engine you stick with how they routed it OEM because that takes into account these "incremental design" decisions.

Although I have seen a piston melt onto the side of a cylinder causing catastrophic failure and the car did have oil...

Edit: also the reason I said you can have positive is that when at full boost you aren't going to get a vacuum in the crankcase relative to ambient... Otherwise you could have used the vacuum generated for the power brakes instead of having to store the vacuum in canisters)

Edit, edit: Maybe I am just dumb... But if the vent had "nothing" to do with lubrication it would have made more sense for the engineers have vented the crankcase on the low pressure side of the turbo since you would have increased the pressure differential between the combustion and crankcase side of the piston increasing power and fuel efficiency while still maintaining emissions.