This still doesn't scream to me "we're gutting the combat system".
An HD remaster of the game would be "just improve the graphics", which would mean flat 2D backgrounds with HD, high-poly models running around on it. The world map would still be a sparse representation of locales, and they'd probably redo FMV's. They'd redo the music and the UI. That's about it.
A remake allows them to rewrite dialogue, make fully 3D, explorable environments with a non-fixed camera, more movement options (maybe there will be hidden chests you'd need to jump to, for instance), enhancements to the combat to make it more exciting (but still ATB/turn based), new towns or dungeons on the overworld, new characters, maybe a new party member, new end-game content (more weapons, maybe adding a boss fight with Genesis), new Materia, new summons, new weapons and items, new minigames, the list goes on and on.
He's mostly addressing purists in that, because there are people who are like "IT NEEDS TO BE EXACTLY THE SAME JUST BETTER GRAPHICS DON'T FUCK IT UP" but there's a wide range of improvements that can be made between that extreme and "make it Kingdom Hearts instead".