The most probable explanation is that someone created a of HeartGold and appended -xenophobia- to the filename as an edgy, attention-grabbing, or thematic descriptor. ROM hackers often add suffixes to differentiate their patches.
While files like the Xenophobia release are historically significant, they are often distinguished from or "Redump" copies: 4780 - Pokemon Heartgold -u--xenophobia-
is the standard chronological release number assigned to it in NDS (Nintendo DS) ROM databases. 📖 The Story of Pokémon HeartGold The most probable explanation is that someone created