Hello,
According to the development team the issue reported in bug number #99934703 is an intended behaviour. When PageSize is large, there will be more rows for Spread to handle. Things such as laying out the Spread, render and synchronize rows, adjust scroll bar thumb, will require longer time to be completed.
Hence, Spread would take more time to load the rows as the page size increases.
Thanks,
Manpreet Kaur