Yes, the feature_flag differences are very frustrating, I've been taken by them in the past as well.
This is why, the major focus at the moment is to fix this. Here they are outlined:
https://docs.google.com/spreadsheets/d/ ... edit#gid=0
tracking the status as we work on bringing in parity.
Then we are working on making ZFS have one repository, with each OS as part of it. There are
huge changes to the ZOL repository, merging in FreeBSD right now, and at the pace they are going
it will be there soon. Once they are done, I will merge OsX into it as well. Suddenly, new feature_flags
will be available to all at the same time.
It is a lot of work, and other development has slowed down because of it, but I'd like to
believe it will be a good thing.