Does the length of an IPCC Scientific report imply anything about credibility or thoroughness? Background

In a question about the Green New Deal, I posted a comment to an answer that asserted the Green New Deal was not based in any science:


  It's not a surprise that such a report [sic: read resolution] is lacking in science.


In context, his statement is referring to the Green New Deal itself, not the IPCC Special Report. In my comment, I mention that the resolution cites the IPCC Special Report on Global Warming of 1.5 ºC. The fact that that the Green New Deal does cite the IPCC report means that it is not utterly lacking in science (i.e. as opposed to citing nothing).  While United States legislation does not have requirements for rigor, my question is about traits pertaining specifically to the special report.  

With regard to the IPCC Special Report, I mention its page length:


  It does include science. The whole resolution is premised on the Special Report on Global Warming of 1.5C which is over 600 pages in full length. I was just curious about an omission of a detail.


My implicit assumption was that the longer the length of a peer reviewed IPCC report the higher its credibility. I am not referring to the Green New Deal; I know united states resolutions do not have any research standard.

That said, given the following comment, I am now questioning the assumption of length in relation to credibility:


  Why is the length of that report relevant?


This comment is what lead me to ask...

Question

Does the length of a peer reviewed scientific report, in this case the IPCC Special Report, imply in any way that it is more credible or thorough in its results?
Very hard to say in general.   A 600-page report could be 600 pages of garbage.  Obviously a super-short report couldn't be very thorough, or contain very much detail/depth. 

If someone said "I have here a 600-page scientific report: is it any good?"  I would have no way to know.

If you want to make a claim for the credibility of IPCC reports specifically, I would quote the Union of Concerned Scientists:


  The IPCC’s technical reports derive their credibility principally from an extensive, transparent, and iterative peer review process that, as mentioned above, is considered far more exhaustive than that associated with a single peer-reviewed publication in a scientific journal. This is due to the number of reviewers, the breadth of their disciplinary backgrounds and scientific perspectives, and the inclusion of independent “review editors” who certify that all comments have been fairly considered and appropriately resolved by the authors. 


Recursively, you would then have to support the credibility of UCS, which Wikipedia (which attempts to be neutral) calls a "nonprofit science advocacy organization".