For over 25 years I've done ~1000+ first ascents with ~100 this year alone on almost every type of stone. Cleaning/trundling loose rock off first ascents is an often overlooked and under appreciated risky part of establishing new routes. It is risky for the person doing it and it is risky for all those that follow if it is not done properly or not done at all in some instances. There is also a fine line between over cleaning for safety and under cleaning for aesthetics (good) and laziness (~bad). Never assume the rock even on established old classics is solid until every hold is searched for visible fractures as well as inspected by hand, knocking and listening as well as feeling for hollowness and vibrations. Even then I have still had seeminlgy solid holds break on me. This dude is lucky this was not worse - be frkn careful; 
https://www.climbing.com/videos/video-boulderer-falls-pulls-300-pound-block-off-with-him/