When virtualization is enabled, only the visible items are rendered in the DOM, and the space for the non-visible items is calculated based on the total number of rows and columns. This approach helps optimize performance by not rendering all the elements at once.

However, the delay you're observing happens because the DOM takes a small amount of time (milliseconds) to render and re-render the cells of the virtualized table as you scroll. This is especially noticeable when scrolling rapidly because the scroll event is triggered at a higher frequency than the time it takes for the DOM to catch up with the rendered elements.