I don't think it's extensive because of the very low sample size, the fact we don't know about each instance and none of it has been corroborated.
I'm also uneasy about letting black people speak for other POCs on this issue. In my experience, racists tend to be racist towards multiple or all other races rather than a single one -- hence why you dismissing other POCs views on it doesn't make sense to me.
Less than 1% is not "extensive" by anyone's metric, either.