Custom Items not showing up unless Experimental Settings are enabled.

I have a small addon that adds some new items. These were all working through the 1.13 beta. Now that 1.13 has officially released, I launched a new world, loaded my addon, but noticed that my custom items only show up when Experimental Settings are enabled. To test this, I simply use /give @s <item name> and this only returns my items when Experimental Settings are enabled. Is this expected behavior? Can addons with custom items only work with Experimental Settings?