Since no one has specifically mentioned it yet.. OpenBSD has had the ability to do FDE from installer since FDE was added to OpenBSD (sometime prior to 2007).. This change makes it more convenient.
Yes, you are correct in the sense that you need to create a partition within which you build an encrypted 'device' before running the installer script. And then at the appropriate point in the installer dialogue you need to select the encrypted device as the target to install to. It is I agree only a few extra commands, but obviously one of the OpenBSD team thought it worth while to automate those few steps for 'common' cases.
Above is the section of the FAQ about full disk encryption for OpenBSD 7.2 which is the most recent release.
PS: I agree fully with a parent comment that the OpenBSD installer is superb. It is like working your way through a checklist. Nice and straight forward once you have read the FAQ first.
https://www.openbsd.org/faq/faq14.html#softraidFDE
Above is the section of the FAQ about full disk encryption for OpenBSD 7.2 which is the most recent release.
PS: I agree fully with a parent comment that the OpenBSD installer is superb. It is like working your way through a checklist. Nice and straight forward once you have read the FAQ first.