Only some years later when I only had an Amiga 2000, I somehow found out that the 1084S IS capable of displaying NTSC, and then found out that some games played faster (or in the case of SotB 2, at the speed it was probably ment). Never bothered to check on Chaos Engine though.
Actually there's not much more than a handful of games on the Amiga originally designed for NTSC (I base this on actual NTSC releases, and those are not many). Thing is, for some reason many developers only used 320*200 of the 320*256 available pixels on the PAL screen. Many games will run in NTSC, but chances are they were never designed to do so. Brian the Lion, for example, runs way too fast when in NTSC, even though the entire game looks like it was designed for NTSC. Many games that looks like they are designed for NTSC even do have title and introduction screens in PAL.
Furthermore, in many cases, if running a game which looks like it was designed for NTSC but actually wasn't, in NTSC mode can make things behave really odd. Jerkyness in the scroll can appear, if the game uses long samples in their modules (if modules is used for the music) the music can sound really bad... and so on...
I have no clue as of why they did it this way, but when talking about games like Eye Of The Beholder and such, it was probably not more complicated than the fact they were ported from a system which used 320*200 as default resolution. Another theory can be that only using that part of the screen could speed things up...
Someone has mentioned this before that when you use Screenmode Prefs or the Early Startup Menu to switch into NTSC mode on a PAL machine it is outputting 60Hz PAL and not 60Hz NTSC.
PAL 60Hz is actually the best of those kind of modes available, as far as I know, because it really is 60Hz and not 59.98Hz which NTSC is. Furthermore, it handles colours way much better than "NTSC - Never The Same Colour". It probably is the way which you've heard... otherwise I would have had real trouble getting anything but an out-of-sync and black & white screen when running my A1200 in the, so called, 'NTSC' mode back in the days when I ran the computer without an RGB cable on a TV which didn't support NTSC.
But, then I must admit that I am curious as of how to get Amigas running on a TV in the US? Are there true NTSC-based Amigas out there? (Besides the A1000)?