in those classes that teach good buoyancy, trim and propulsion techniques, how much time is spent on those skills?
The OW class we teach through the LDS has nine hours of pool time, spread over six sessions. With the exception of the first one, in which much time is spent on swimming, snorkeling and free-diving, our pool sessions consist of having the students swim around the pool in buddy pairs. From time to time, Peter will take a buddy pair off to one side to demonstrate skills to him. Any skills the student has demonstrated to Peter are fair game for the rest of us CAs to request during the free swimming time.
So I guess I would say that 90% or more of our pool time is spent on neutral buoyancy, trim and propulsion . . .
On another topic, I own a jacket BC. I use it in the pool. I have no more difficulty achieving neutral buoyancy and good trim in it than I did in my backplates. It took a bit of experimentation with weighting, tank position, and fin choice to get it perfect, but it was doable. (It took the same kind of experimentation with my backplate setups.) If the gear fits you reasonably well, and you are properly weighted, and you have placed those weights correctly and are utilizing the right posture and the right fins, it's possible to trim out in almost anything.
I don't LIKE the jacket BC for a whole raft of reasons, including the fact that it doesn't hold a tank as stable as a backplate does, that it has all kinds of crud on the front of me, and that I need a chest strap that it doesn't have to keep the shoulder straps from sliding off my shoulders. I dislike the placement and paucity of attachment points. But I use it in the pool so I look like the students, and I will definitely say that I can trim out in it.