The condition of the slab decides the result more than any step in the process. A polished floor shows the concrete that was poured: its flatness, joints, patches and cracks all come through, and polishing does not level a floor.
A newer builder slab
Timing and mix matter in a house that is new. Commercial specification guidance asks for a slab at least 28 days cured before polishing, notes that curing compounds can slow drying and discolor the surface, and prefers a vapor barrier under the slab. Admixtures can cause color variation, and a mix with portland-limestone cement, a high water-cement ratio or bleed water finished into the surface can leave a weak one. Residential builders may not pour to that specification, so a builder slab is not guaranteed to match it. If you are building or buying new, ask the builder what mix and curing the slab had, and keep storage and taped-down protection off the floor.
A slab under carpet or tile
An older floor has been covered since the house was built. The covering comes off, glue and thinset are ground away and the surface is tested for hardness before polishing begins: ACI 310.1 calls for a Mohs hardness above 4. Cracks, saw-cut joints and old patches stay visible once polished, so they are filled or repaired and not erased.