So far as I am aware, following a search of the documentation and the code, this is not a feature that currently exists in Indicia.
There would be several approaches to implementing it. The following come to my mind.
1. A completely generic solution built in to the warehouse which adds a default_sensitivity_precision to the taxa_taxon_lists table. This value could be configured in the warehouse interface and would be applied to all incoming records of a given taxon if no other value is supplied in the submission.
2. A client-side solution in which an additional option is added to the configuration of the recording form that allows a list to be supplied of taxa and their default sensitivity_precision. You could choose to allow recorders to override this if you wanted them to have that option.
3. On the client-side, sub-class the dynamic_sample_occurrence prebuilt_form (if that is what you are using) and override the get_submission() function where you can hard code the values to submit. This is the quick and dirty way.
You definitely want this to occur at the point the record is created in the warehouse so that the sensitivity_precision is stored in the occurrences table and the blurred public_geom is calculated and stored in cache_occurrences. You want the blurred location to be cached for speedy reporting and not calculated when the records are requested for display.
Hope that helps,