Saudi are speaking to several audiences and probably seeking to confuse them all, probably succeeding, too. The odds on there being as much as a new Ghawar as yet undeclared are pretty low (though, if it happened we should probably rejoice and get on with reshaping ready for peak oil a couple of years delayed).

Think about their audiences and what effect such comments are intended to work on them. Think about their objectives: survival until their emperor's clothes are revealed, secure futures thereafter, protection meanwhile. Until Saudi reserves are given proper public scrutiny I would treat all their utterences as intentional obfuscation. That may help explain your puzzlement, HO.

I have seen no detailed attempt to refute Matt Simmon's analysis, just vague and inconsequential mutterings, so I would say that Matt is most likely correct until convincingly shown otherwise.

You must have missed the refutation by the petroleum engineer, Jim Jarrell:
Another  Day in the Desert: A Response to the Book, Twilight in the Desert

Simmons himself admitted recently in Barron's that Jarrell's analysis is excellent, but said that Jarrell made one critical mistake: Simmons says he never claimed that Saudi Arabian production is facing imminent collapse.

Has anyone actually seen his report?  I tried emailing him and calling him, but no reply.  After the whole CERA thing, I'm pretty dubious about analysts and consultants who make a big fuss in the press but won't submit their methodology to any realistic public scrutiny or answer questions about any potential conflicts of interest they might have.  My main reaction to the public coverage was that it sounds like he's assuming that everything the Saudis say is true.   Of course, if you assume that going in, then you're not going to find any problem...  But it would be interesting to be proven wrong.
Tim Wood from Resource Investor told me that the report is only available to paying customers. Lynch and Simmons have both seen it. Simmons' comments on the report are also behind a paid subscription wall at Barron's, although I saw the quote before it was removed at peakoil.com.
I'd seen brief mentions of Jarrell's refutation but no proper detail. The article you cite, JD, is the most detailed I found online and that is little more than hearsay IMO.

Via Jarrell's company site ( http://www.rseg.com/ ) I found a link to this pdf of a newspaper article:
http://www.rseg.com/pdf/Globe11_14_05.pdf
but the most informative info in that was:


He [Jarrell] reviewed several of the key papers that Mr Simmons relied on heavily to come to his conclusionsbut Mr Jarrell arrived at a very different finding.

"I got a comfortable feeling that [Saudi Arabia has] an unprecedented record of reservoir operationsand management ... reserves are not overstated, that production is unlikely to collapse ... "

So that's alright then, we can all go back to sleep for a couple more decades.

The best detailed Saudi info I could find to refute Matt Simmons was this presentation from February 2004:
http://www.saudi-us-relations.org/energy/saudi-energy-reserves.html
Specifically this talk:
http://www.saudi-us-relations.org/energy/saudi-energy-saleri.html#Read
and its slides pdf:
http://www.saudiaramco.com/sa/webServer/general/Presentation_Fifty_Year_Crude_oil_Supply.pdf

I must admit I am still somewhat confused by what exactly they mean by 'contingent reserves' and I am very wary of Saudi fields actually producing 75% of OIIP. I do note that they are very leery of producing more than 12mbpd (from 2016) and, as we all know, that won't be enough even before 2016 unless massive demand destruction takes place.

A few other sites about Saudi you might find useful:
http://www.saudiaramco.com/bvsm/JSP/home.jsp  (Saudi Aramco, though I found nothing useful there)
http://www.sgs.org.sa/index.cfm?sec=1&page=home.cfm  (Saudi Geological Survey, much more interesting)
http://home.entouch.net/dmd/Oilcrisis.htm  (Glenn Morton's oil crisis site)

I'll stand by my comment above until I see proper, independent, data and analysis to the contrary.