"Hardened Prestige" is not a standard industry term. It appears to be community slang, a specific modpack name, or a misinterpretation. Based on the words, here are plausible meanings:
Default balance: checkpoints, difficulty sliders, accessibility options, progression persistence, broad appeal
Provide context: Where did you see this term? (Reddit thread, YouTube video, mod site, specific game wiki). With the source, I can define it exactly.