He should reveal information as and when it's needed. Not spill everything in one debrief session.
He knows this universe is altered, he has no idea how telling everything may further change things. And he has absolutely NO guarantee those changes would be for the better.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist