Oprah Winfrey is holding back about Lance confession

According to TMZ, Oprah Winfrey is already talking about her 2-and-a-half hour "confession" interview with Lance Armstrong ... except she's not exactly revealing what he said to her.  Oprah appeared on "CBS This Morning" to talk about the sit-down ... but nobody on the set -- including anchor Gayle King -- really pushed her about what Lance said.

Oprah DID say Lance confessed about using performance-enhancing drugs during his cycling career ... but added, "He did not come clean in the manner I expected."

But nobody followed up with questions about WHY Lance's answers were so unexpected.
Here's what we do know:

-- Oprah says she prepared 112 questions for the interview, and got through most of them.
-- Oprah says "there were times" Lance got emotional, but she didn't drop details.
-- Oprah says she was so tough with her questioning, that Lance asked her to lighten up.
-- After the interview, Oprah says both she and Lance were exhausted and satisfied.
-- Lance's lawyers were NOT in the room during the interview.
-- Oprah suggests Lance's people leaked details about the interview to the AP.

The Oprah vs. Lance interview is set to air Thursday -- no word if Oprah plans to release any clips of the meeting before then.

Our question -- why the hell did the execs at CBS News let Gayle -- Oprah's BFF -- conduct an interview with this kind of news significance knowing she wouldn't push her hard?