Why SR-IOV Shared Port and not vSwitch?

Hello,

I was looking into the InfiniBand SR-IOV implementation and as I see here:
https://www.mail-archive.com/[email protected]/msg11956.html
the shared port model has been implemented in the drivers.

In an ~5 years old presentation from Liran Liss
(https://www.openfabrics.org/index.php/ofa-documents/doc_view/255-infiniband-and-rocee-virtualization-with-sr-iov.html),
the virtual switch model is briefly mentioned as well.

The disadvantage of the virtual switch model (that is mentioned in the presentation as well) is the bloated LID space. Is there any other good reason (or great disadvantage of the the vSwitch model) that the shared-port has been chosen in favor of the vSwitch?

Vangelis