Any references to the data page by the section will cause the data page to load if it isn't already loaded when the section is displayed. I suspect this is what is happening as you flush the data page before refreshing the section. A couple of high level thoughts you could explore:
You could potentially use a condition for the display of the fields that reference the data page so it does not display after clicking the "Clear" button, perhaps by setting a flag when you click "Clear" that tell those fields not to display.
You could potentially use a condition for the data page itself, to change what data loads after clicking the clear button, perhaps by using a similar kind of flag as with the above option.
Use two mutually exclusive (visibility condition wise) Layouts for search results:
Layout 1 - Use a when condition to show this layout when none of the criteria is entered. This layout will have a label that says : No records found.
Layout 2 - This layout will hold your repeat grid (search result). Use a visibility when condition to show this layout when at least one of the criteria (or whatever be the minimum search criteria) is entered.
Both layouts should be inside your current result section. And, make sure that you have 'Disable automatic refresh' option ticked on your Grid repeat layout property.
This will help PRPC to dynamically choose between layouts depending on context, and avoid loading your data page unnecessarily.