Impaling Enchantment issue

I was told to file this as a bug by Fanny Vadillo Herrera in the Slack channel for requests. It seems impaling only works on aquatic mobs when they are submersed under water. Yet when on land, the enchantment is useless. Why is this? We are looking to add this enchantment as a "custom" 3rd type of enchantment for a new type/class of mob we are making but are hindered at making this enchantment useful on land when it only works while underwater. According to the wiki, java only requires the mob to be aquatic based, no water required.