I agree with this. I think it's a softly softly approach by LE by using this new tactic of just BL's dad and one officer.
It will be seen as less of a perceived threat by BL, if he is in there alive.
A massive ambush by armed officers could lead to a shoot out (if BL has a weapon) or suicide by cop, or suicide by his own hand.
It is a far less menacing and intimidating presence for there just to be one officer and BL's dad.
My thoughts are that LE spoke to the Laundries and said,
"Look, we now have strong reason to believe he's in this particular area, and we believe he is still alive. If we go in there without you, there's a high probability BL won't come out of there alive. This is your chance to change that and ensure he does come out of there alive. You can reason with him, you can talk him down. Work with us to prevent another unnecessary death"
MOO