Apple abandoned ZFS when Steve Jobs was still alive. Larry Ellison has frequently described Steve Jobs as one of his best friends whom he frequently went on walks with. The idea that Steve could not have gotten Larry to license ZFS seems crazy to me.
I'm sure the lawyers were not too keen to depend on a personal relationship to smooth over their dealings with Oracle, a company known in large part for suing people in novel ways.
I used OS X Server in 2008. It had major quality issues that seemed to only get worse with subsequent releases. Several advertised features accessible from the UI didn't work or straight-up broke things. I doubt Jobs paid much attention to it.
Why would you think he wasn't? Many anecdotes mention him micromanaging minute details, and many of the things he mentions in keynotes are highly technical as well as low-level.
