Yes and no.
Yes, its there for a reason and probably adds some rigidity to the suspension and protection but its not going to create a dangerous situation if the support or the plate is removed.
Last year at AutoClub Speedway I went off track and bent the rear plate. Back in the paddock, we removed it in a few mins and I raced the rest of the weekend without it. There was no change in handling even at 135mph on the NASCAR banking. I did replace it before the next race mostly because removing it may not be a legal modification in Boxster Spec.
There is a discussion of this plate in the middle of this thread:
A shoutout for the technobrace and Pedro.