Can the truth be compromised?

I am much confused with the end result of the petition before the Supreme Court filed by CHED Chairman Romulo Neri, who had asked that the Senate be prevented from compelling him to testify on the ground of executive privilege.
During the orgal arguments, the Supreme Court apparently issued a solomonic solution by urging the parties to come up with a compromise.
As I write this, the compromise was that Romulo Neri will go back to the Senate and testify, but the Senate cannot ask three questions.
These forbidden questions, according to news reports (since I was not able to attand the oral arguments at the Supreme Court), are: (1) Whether President Arroyo approved the NBN-ZTE project inspite of the bribery disclosure, (2) whether she had dictated on Neri to approve the project, and (3) whether the President had followed up on her directive.
To, me this is a highly unusual result in the highest court of the land.
It is my impression that the truth after all, is subject to compromise.
So the people will not know the answers to the forbidden questions from the very lips of Romulo Neri.
But of course, the answers are already out, mainly from secondary sources like Rodolfo Lozada, Jr.
Lozada has testified that Neri had told him that the President instructed Neri to approve the monumentally anomalous NBN ZTE broadcband deal.
In fact, I recall Neri had already testified in the Senate that the President had told him to reject the P200-million bribe offer of Benjamin Abalos, but approve the NBN deal just the same.
But I am very uncomfortable about this proposed compromise deal to be struck in the Supreme Court.
I know as a lawyer that almost everything can be subject to compromise.
Under the rules of court, the few things that cannot be subject of compromise are support, civil status of persons, among others.
But never did I ever think that the search for truth, or the truth itself, is subject to compromise.
The reason why I think the truth is not subject to compromise is that one is supposed to tell the truth, the whole truth, and nothing but the truth.
With this looming compromise deal, it is my undertantding that when one testifies, he may testifiy about 90% of the truth only.
So when Neri goes back to the Senate, he will be asked to tell the truth, most-but-not-all of the truth, and nothing but most-of-the-truth.
Funny.
I was expecting a landmark, historic decision by the Supreme Court on the issue of executive privilege, in the same way that the United States Supreme Court decided executive privilege in United States versus Nixon.
During the politically tumultuous times of the Nixon presidency, Nixon had wanted to prevent the White House tape-recordings of presidential conversations revealed to the public.
Nixon failed in his bid.
Eventually, he resigned from office.
I had also wanted to know whether Neri can invoke executive privilege, when he is not the president.
Who has the privilege to invoke executive privilege?
Who decides what is covered by executive privilege?
Can executive privilege be invoked, even if raising it would effectively conceal a crime?
Can anybody, who might just happen to have talked with the president, be allowed to invoke executive privilege?
If the President talks to a Malacanang gardener, can the gardener refuse to disclose his/her conversations with the President on the ground that in his personal judgement, the conversations were matters of executive privilege?
Is it the garderner who decides what is covered by executive privilege?
In short, what are the parameters of executive privilege?
The Supreme Court is the court of last resort.
With this compromise agreement (if executed), there will be no definitive ruling on the matter of executive privilege.
For the Supreme Court, it would have been a defining moment.