To better explain about this collection, a dude named Christian Whitehead who would later go on to make Sonic Mania decided that he wanted a definitive version of Sonic CD. That means both English and Japanese soundtracks, high-res anime cutscenes, instant load times, no slowdown, and widescreen. In order to pull this off he had to reverse engineer the games and rebuild them from the ground up. He succeeded and this version of Sonic CD is widely praised. He later went on to give the rest of the Genesis Sonic series this treatment from my understanding and now they're putting this on modern consoles with a couple bonus features like new animated cutscenes and new stages and stuff. The collection ALSO contains regular emulated versions of the games too.
However someone at SEGA needs to be fucking fired because that chart makes the situation look exponentially worse than it actually is. SEGA later updated the chart but it's still awful. All it really says is "If you preorder you get 100 Bonus Coins and Mirror Mode unlocked from the start" and "We'll be selling Hard Mode missions and extra music at a later date which is included in the Premium Edition". But they cocked it up by making it LOOK like there's a million slightly varied versions when there isn't.
It's like someone at SEGA saw Ubisoft game sales and thought "AH! I guess those preorder charts must have helped with sales! We need to make one just like that!".