I don’t know why this would be surprising. They’re not gonna exactly throw everything away and start over, are they? Just like the Source engine is derived from

I don’t know why this would be surprising. They’re not gonna exactly throw everything away and start over, are they? Just like the Source engine is derived from the “GoldSrc” engine, which is the terrible name for the engine that Half Life used, and that engine is derived from the Quake engine. You only make the changes necessary to update it for new hardware. For example, you throw away the old BSP rendering code, as elegant as it is, because it’s designed to get good performance on a Pentium 90 and modern computers just aren’t like that. It’s the ship of Theseus.