If they tested against the 2009 Cayman S, the Z would have been creamed. Against the 08 Cayman S it was able to hold its own. But it would have been more competitive if not for the heat issue.
R&T exposed the Z's overheating oil issue. As noted in this thread, this issue is the Z's "achilles heel":
First track experience today ! Some good, some really bad
It seems this test car was not one of the early "ringer" press cars which had oil coolers installed. Nissan needs to fix this on the 2010 cars, otherwise the Z will not be track competitive!