"But Janssen said Paul van der Sloot was detained for being a suspect in the disappearance, not for obstructing the investigation."
And yet, during his detention he was NOT interrogated by police. He made (1) initial statement to police upon his arrest, and that was it. In my opinion his arrest was a ruse. An appeasement of sorts.
And, now, he is allowed to see joran. Why?
Exactly right. They have permitted (dare I say aided?) in letting this case slip awway.