Can't use Linux distribution tools like apt/yum unless you package the update contents as rpm/dpkg files and distribute apt/yum with the base system. Neither of those is happening in OpenBSD, or likely any BSD. (I can go into more detail on why if you're curious.)
In some ways, the BSDs are just catching up to Linux in terms of update distribution mechanism. They all have a history of being self-hosting compile-from-source systems, and some greybeards are still pretty attached to that idea.
As someone who discovered Linux first and happily used it for many years before discovering the BSDs, I think there's a lot Linux gets right that BSDs will or should adopt to be relevant. (There are also many things the BSDs get right, of course.) This is a good example of that.
Using pkg to update both base and ports with a single tool will be nice. As will updating jails robustly; freebsd-update is not so great in jails in my experience.
The place people usually trip up is with freebsd-update getting confused about what version it's trying to update. The '--currently-running <release>' option is your friend here.
In this case it's just about sane defaults and options. You could take any binary-update Linux distribution and update from source yourself if you wanted to. It was always an option. All of the build machinery and sources were published from the beginning.
With the BSDs, you didn't even have the option of binary updates or packages until quite recently.
In some ways, the BSDs are just catching up to Linux in terms of update distribution mechanism. They all have a history of being self-hosting compile-from-source systems, and some greybeards are still pretty attached to that idea.
As someone who discovered Linux first and happily used it for many years before discovering the BSDs, I think there's a lot Linux gets right that BSDs will or should adopt to be relevant. (There are also many things the BSDs get right, of course.) This is a good example of that.