Afraid no parameter available here in this scenario.
If data was been displaying in an ALV Grid - would have more influence.
See the note:2041946 - ALV Gridview Control: Scrolling on demand enabled by default
Reason for suggesting to test directly via WEBGUI was to see if NWBC Framework was having an effect here.
Your assumption re information not been buffered is correct
Chrome/Firefox browser may offer better performance.