Vacuum hose to oil filler neck?

For the Series II (and I believe the later S I) they added a vacuum hose from the intake nipples (by the washer fluid bottle) that leads to the top of the oil filler neck. What's the point of this? It seems it's lowering the pressure in the oil chamber?



edit: I'm asking because I'll be Seafoaming my car. Those are the nipples recommended to use to inject the SF into the engine, I believe I should be able to use that hose as it's easier to reach and connects to both nipples and nothing else.