IIRC, BC was never officially named a suspect or POI.
IIRC the issue with declaring someone officially as a suspect, or POI was that it would (or might) obligate the prosecution to share more info with the defense/defendant prior to any subsequent arrest. [ I'm a little fuzzy on it, and it's based on memory of what others on WS who seemed knowledgeable enough at the time were posting...]
Clearly LE was 'interested' in him from at least the time of discovery. Declaring him officially as such though would have supposedly 'tripped' something 'official' that LE didn't see the need to trip. [ again, just going off memory from some of the 2008 discussions... ]
"They're taking his kids, but LE isn't even officially stating they're interested in him..."