It's about the most un-secret 'Secret' in the world, and the report is something like 18 years old. It's a symbolic slap in the face, yes, but not an actual security compromise.
The most instructive thing about the Israeli program (Don't know if it's covered in this particular report, it's been known for a long time) is that they completely outfoxed all the watchdogs and interested parties (Including us) by building several undisclosed levels down below the ones that were known, where they conducted all the work that might have gotten the non-proliferation community on their asses...which tells you a lot about how effective monitoring, inspection, and surveillance are when the guys being looked at have something to hide.