Arcana of the ports build system

From: George Mitchell <george+freebsd_at_m5p.com>
Date: Mon, 06 Jan 2025 13:05:31 UTC 
/usr/ports/editors/abiword/Makefile includes these lines:

COLSERVICE_BROKEN=              Does not build with asio from system
COLSERVICE_BUILD_DEPENDS=       ${LOCALBASE}/include/asio.hpp:net/asio
COLSERVICE_LIB_DEPENDS=         libsoup-2.4.so:devel/libsoup \
                                 libgnutls.so:security/gnutls
COLSERVICE_RUN_DEPENDS=         ${LOCALBASE}/include/asio.hpp:net/asio
COLSERVICE_CONFIGURE_ENABLE=    collab-backend-service

Now in fact I have net/asio installed, and /usr/local/include/asio.hpp
exists.  But attempting to build abiword stops and complains:
Does not build with asio from system
As far as I can tell, no such thing as "asio from system" even exists.

Can some generous soul kindly shed some light on what's intended here?
Thanks, and Happy New Year!                                  -- George