Re: makefile-mode font-lock bugs and annoyances

[Richard Stallman]

    The problem here is that for backwards compatibility gmake will read in 
    a Makefile when there is no GNUmakefile. That made some people get 
    sloppy and actually write gmake constructs into plain Makefiles.

This is not incorrect.

In general, I think you are trying to reason theoretically
about what font-lock should do in Make mode.  But practically speaking
people don't like the results.