Epic was very much released, it is one of Amiga’s last big games.
Epic had a Cyberpunk 2077-style cycle of hype: massive coverage, last minute delays, misleading advertising and troublesome review process, and eventually backlash from consumers due to poor debugging and running poorly on the A500 generation (it fared much better on A1200). It was successful enough to get a DOS sequel in 1994.
I assume the "unreleased” part pertains to the track itself. It probably was meant for a cancelled Amiga CD32 conversion.