I think that may be a bit of an unfair statement. They do note just above in the public instances the following:
> Note: Use public instances at your own discretion. Maintainers of Whoogle do not personally validate the integrity of these instances, and popular public instances are more likely to be rate-limited or blocked.
Having tested with various search strings, the time to first search-result paint for the the first public instance [1] feels just as fast a Google.