You are able to open to LAN and change the gamemode to survival and even enable cheats this defeats the whole purpose of Hardcore
Environment
java version "15" 2020-09-15
Java(TM) SE Runtime Environment (build 15+36-1562)
Java HotSpot(TM) 64-Bit Server VM (build 15+36-1562, mixed mode, sharing)
Duplicate of MC-134, which is working as intended.