My belief is that BL's parents (or at least one of them), believe every word their son says and take every word at face value. They probably have since the day he spoke his first words. That's why he lives at home, has no visible means of independence and probably has 1000 reasons why he can't work, won't work, shouldn't work, can't work. That's why I think they called their lawyer friend in NY because they believed every word of BL's story and wanted to get guidance on how to protect him because they believed he was innocent of whatever he was afraid LE would think about this situation.
So when he said he wanted to go hiking and he said when he would be back, they took him at face value. Believing he was innocent, they didn't think much of his hike.
I don't think they are calculating, shrewd, deflecting or buying BL time. I think they just have this default mode that leans toward believing their son is misunderstood, innocent and never in the wrong. Everything is everyone else's fault when it comes to him. They feel sorry for him and try to help him out and do what he asks them to do without question.
I think many of us know people who are like this when it comes to their children, maybe not to this degree, but pretty close.