If a package was looking for an older library, then that package was out of date, this happens as the packages aren't built at the same time as snapshots so you often need to use the ports tree yourself when following them.
The major number of a library version is cranked whenever an incompatible change is made, and programs need to be relinked,
13.0->13.1 is safe,
13.0->14.0 is not.
The nawk change is recent, awk is no longer linked to nawk in -CURRENT.
http://marc.info/?l=openbsd-cvs&m=128276412305891&w=2
http://marc.info/?l=openbsd-cvs&m=128285071411286&w=2