Can you let me know, the document name and section are you referring?
In the paragraph, it is recommended to use buffer ICs on the carrier board with the HSYNC and VSYNC signals.
If you refer the Colibri Evaluation board V3.2 schematics, you can find IC25 and IC26 (SN74LVC1G17 - Single Schmitt-Trigger Buffer) in the VGA schematics page. IC25 and IC26 are the buffer ICs.
Let us know, if you have any further query.