I used the GTNHConventions plugin in my project with enableModernJavaSyntax enabled, and when I tried to test it outside of the development environment, the methods I invoke did not seem to be remapped to what Forge uses in actual production.
However, when I disabled enableModernJavaSyntax, and of course used Java 8 syntax equivalents, the method was correctly remapped.
I used the GTNHConventions plugin in my project with enableModernJavaSyntax enabled, and when I tried to test it outside of the development environment, the methods I invoke did not seem to be remapped to what Forge uses in actual production.
However, when I disabled enableModernJavaSyntax, and of course used Java 8 syntax equivalents, the method was correctly remapped.