Snapshots in the AsciidoctorJ side don't use the lastest master from Asciidoctor core. AsciidoctorJ (and plugins) only use stable releases of Asciidoctor core. You'd have to clone the Ruby version and test that directly to know if it fixes it. I recommend testing that scenario outside of using AsciidoctorJ or the plugin.
We need clear instructions on the AsciidoctorJ side of things about how to test a local install of Asciidoctor core. We don't yet have that.
-Dan