For sysadmins who closely follow the "recommended" way, having to migrate the configurations of the http server twice within half a year must have been a frustrating experience.
Also, I wonder what "removal from base" means exactly - can you still install them (the OpenBSD-patched versions) from the ports collection or something like that?
Sysadmins had ~2 years to migrate from Apache to nginx (and if they didn't want to migrate, they could continue to use Apache from ports).
For nginx, they only had 6 months to migrate (though again, they can still use nginx from ports).
So no, they didn't have to migrate the http configuration twice a year, more like twice in 4 years, although, considering that OpenBSD only ever included into base 3 web servers, more like twice in 16 years.
Not being in the base means that it doesn't get the same security attention as its not officially part of OpenBSD anymore.
Does "before" refer to the period before Apache was dropped from and nginx was imported to base? (Since apparently you can just use nginx from the base when it is there.)
EDIT: It just occurred to me that "complex setup" likely indicates that you would like to change some build flags, so you have to install from the ports. Stupid me.