This was my impression as well after using OpenBSD, and when I pointed that out a while back on HN, it was pointed out that the core linux manpages have gotten much, much better in many cases[1]. In that respect, it may be another example of the GP comment.

1: My go-to example was always ifconfig, but linux's manpage for ip(8) really isn't that bad, as is actually the linux equivalent. Quality probably varies quite a bit based on the package that supplies the utility though, while OpenBSD's quality is fairly universal.