Well, all these effects are common in today's games. Back in 2000 It would have been surprising to see things like this with the HL1 engine. The fact is, since it's modified, it's no longer the same engine, so I don't know what fuzz is about... The interesting thing about the old engine is pushing it to its limits, accomplishing things that were possible in 1998 but nobody had thought about.
All of those effects can be done in Source with a very good performance.
A game engine has limits on what it can draw even if your computer exceeds the requirements. That's why the same huge map in HL1 will give you worse framerates than the Source version, even in the exact same computer.
Take a look at this "diagram" I made
As you can see, there's a certain relation between what you can do, what your computer can do and what a particular game engine will let you do, all in the same system.
Anyway, I do like the screenshots. They make me want to play the Black Mesa mod for Source!!
Edit: if you try to make your imagination overflow the engine limits, the engine will overflow your computer!