Yes, the truth behind Black Cat's Heart Understanding Ability is likely "changing the flow of time." By making time flow at different speeds in various areas, a multitude of strange effects are achieved.
"Space traversal" isn't true traversal; it's achieved by changing the flow of time in different areas, causing light to delay or even deflect. "Object disappearance" isn't the erasure of concepts, but through the acceleration of time in specific areas, causing decay and eventual disappearance. "Thought obstruction" and "magic power delay" are because Black Cat's previous attack delineated different regions within Emerald Sparrow's Magic Body, causing time flow discrepancies among those regions, thus information and Magic Power transmission are still hindered even within the Magic Body.
And if following this route further, Black Cat could potentially achieve even more...
—"Worthy of being the Captain, even in this situation you're analyzing my ability."
