White what you say is true, I feel like this has more to do with their engineers being better at or more comfortable with FreeBSD or something like that.
I'd say we don't know unless we ask Netflix engineers but the comments about license look like a good one to me. Then there is in my opinion the "bloated" Linux versus the more clean BSD experience (I am a Linux user and I like to tinker with BSD sometimes). Maybe it is still true that BSD will not run on as much hardware as Linux does but have you ever compiled a custom kernel on BSD and compared it to compiling a custom kernel on Linux ? On BSD it is in comparison much easier and the documentation is usually really good.