When having a filtered content aggregation, you will have "generally" 20 call to news-abstract.xsl that will call each time

<xsl:import href="docbookenhancement://docbook2html.xsl"/>

BUT this call is quite long, and avoid it in this case (where we do not have any richtext) is really increasing the render speed.

SOLUTION 1 : make docbookenhancement://docbook2html.xsl faster (no need to think for people, no need to migrate)
SOLUTION 2 : avoid this import when not necessary (need to think and migrate)