From https://docs.google.com/document/d/1-EddxCX37fmql_3pO8oCme8zAb2mmAshV4-m4KRo3Kw/edit?tab=t.0#bookmark=id.wb85v1ont85 

We’d like to inform users who are used to our usage of EJSON about the change and allow them to adjust their workflow easily. While we cannot detect with 100% certainty whether the input was intended to be interpreted as EJSON or not, we can achieve a high degree of accuracy by trying to detect EJSON and giving the user the option to convert. This approach has been prototyped out in this branch in the Compass repository.