Why is the open accesss debate not conducted openly?

A curious anomaly strikes me as I update the post in this blog that lists submissions to the House of Commons Science and Technology Committee Inquiry into Scientific Journals that are available online. Several organisations have not put their submissions on their web sites, including CILIP , CURL , and SCONUL , although many others have (see elsewhere in this blog. I contacted these three organisations (and JISC as well who are supposed to have made a submission, though it's nowhere to be found on their web site, and they haven't yet replied). They all explained that the Clerk of the Committee forbids the publication of evidence until the Committee has completed its discussions. This seems odd: I can, to an extent, understand the committee's concern about the publication of versions of oral evidence, which could diverge widely. But if an organisation or individual writes evidence for the Committee and chooses to publish that evidence elsewhere, why shouldn't they? Have they signed away their intellectual property rights to their thought by submitting it to others? Submission to a committee, even a committee of the House of Commons, is surely an act of publication, and unless I sign a particularly restrictive contract with a publisher, I do not lose my IP rights when I publish a book or article, indeed I would expect them to be recognised and protected.
Further, while there may be understandable procedural, historical and constitutional reasons why the committee may wish to control the way in which evidence is published, it seems odd to insist on these when the subject of debate is open access to scientific knowledge (and odder still for organisations with some claim to be interested in freedom of information such as CILIP to acquiesce). It seems to me that this attempt at censorship or self-censorship is in any case a dead letter: both my list and BioMedCentral's list a number of submissions, I would guess that between us we have the majority and I haven't heard yet that any of the authors have been conducted to Traitor's Gate by river.