>>To my understanding, they should import CFLAGS from mk.conf and add to 
>>them if needed. Not the other way around.
> 
> OK, and how is this being done correctly?

The package's Makefile includes bsd.prefs.mk with
.include "../../mk/bsd.prefs.mk"
and then adds to CFLAGS with
CFLAGS+=

The scenario you describe would occur if the package
set CFLAGS _before_ importing bsd.prefs.mk.
Especially since CFLAGS in mk.conf is usually set
with "=", not "+=".


- IT