I agree with this. IMO, MPD believes they know who the killer is, but currently has a primarily circumstantial case. Therefor, they are working to gather enough evidence to be more confident in an arrest.
SGs interview tells me that he believes he knows exactly who the killer is. The drugs/drinking comment was interesting in that it sounds like he or his daughters have reached out to students who could help prove/disprove something (such as an alibi) but students are scared to share info or evidence as they are fearful of personal blowback due to being around or on drugs/drinking. As an adult, that seems silly to me, but I remember being a college student, and I wouldn’t have wanted my name being associated with hanging out with people doing coke or Molly all night - especially in the day where info that hits the internet is potentially forever.