In October 2020, following security disclosures by the Google Security Team, Privacy Badger changed its default behavior. While it would previously learn to block new trackers heuristically after installed, it now defaults to blocking only trackers it already knows from automated testing before release. While it can still be configured to learn heuristically, it is no longer the default option because it can be exploited by third-parties to fingerprint the user based on trackers it blocks.
So it seems that it no longer actually "learns to block", not by default.
In October 2020, following security disclosures by the Google Security Team, Privacy Badger changed its default behavior. While it would previously learn to block new trackers heuristically after installed, it now defaults to blocking only trackers it already knows from automated testing before release. While it can still be configured to learn heuristically, it is no longer the default option because it can be exploited by third-parties to fingerprint the user based on trackers it blocks.
So it seems that it no longer actually "learns to block", not by default.