Unlike the daily death stats, the ONS analyses not just the official cause of death, but also where COVID is listed as a contributory factor - which may not need a test
However, look at the total death graphs:
Once the COVID deaths dropped right down, so did total deaths and they are now almost normal for this time of year.
If there was some other mysterious cause of some of the 67,000 excess deaths, then it disappeared as COVID fell off.
The ONS analysis was that the official figures miss deaths where COVID was at least a significant contributory factor.