As for the DVD release in 2021, it's likely that "Prison Heat" was re-released as part of a budget-friendly, cult classic, or exploitation film series. Many low-budget and cult films from the 80s and 90s have experienced a resurgence in popularity, thanks to the nostalgia of audiences and the ease of rediscovery through online streaming platforms.
As for the DVD release in 2021, it's likely that "Prison Heat" was re-released as part of a budget-friendly, cult classic, or exploitation film series. Many low-budget and cult films from the 80s and 90s have experienced a resurgence in popularity, thanks to the nostalgia of audiences and the ease of rediscovery through online streaming platforms.