A new behavior is consistent with the other optional dependencies.
The source code contains #if ENABLE_ZMQ lines only:
$ git grep ENABLE_ZMQ -- src/*.cpp
src/init.cpp:#if ENABLE_ZMQ
src/init.cpp:#if ENABLE_ZMQ
src/init.cpp:#if ENABLE_ZMQ
src/init.cpp:#if ENABLE_ZMQ
src/init.cpp:#if ENABLE_ZMQ
Change in description line -- "Define to 1..." --> "Define this symbol.." -- is motivated by the fact that the actual value of the defined ENABLE_ZMQ macro does not matter at all.
Related to: