My own personal experience with small cap biotechs is CONTRARY to what you've stated:
With sad reference to AF... When defined as under $350 mln market capitalization I find FEW that have 50% instl ownership UNLESS they were the likes of KERX; SRPT(which AustinMedia inappropriately compared with NWBO!);DSCI;ACAD etc.
Why instl are excluding NWBO goes back to my Aug '14 post on: Why Institutions own less than 13% that was in response to 2OOK+ NWBO owned by poster BasinStBlues: DNDN blighted the entire Immunotherapy landscape since 2006!! with their failed strategic BLUNDERS of major manufacturing cost OVERRUNS caused by how their technology is applied: cumbersome; not fully powered; requiring specialized application etc.