Thanks for the report and looking into the code. There have been previous reports relating to targets and conditionals, e.g., https://debbugs.gnu.org/cgi/bugreport.cgi?bug=13940 (from 2013 ...) and I think it's been mentioned in mail and elsewhere, too.
Updating the doc is no problem, thanks. But I'm not sure how to do a real fix. The conditional might be defined at configure-time, so automake can't know whether it's true or not when it's running, as far as I can see. Maybe you or someone else has a clearer idea of how to proceed? --thanks, karl.
