In MC 1.12.1, HHT items are appearing in all creative tabs. This issue also appeared in McJty's OneProbe, the cause and commit with solution is available here: McJtyMods/TheOneProbe/issues/169. Basically you need to check this.isInCreativeTab(tab) in getSubItems() before adding items to the tab.

Thanks.

I think its fixed in e38d8c4. Uploading a build to Curse...