Custom field sets created for Activities of type Phonebank, Walklist, and Survey don't appear on Advanced Search page

When you create custom field sets - where the fields are configured to be searchable, for Activities of type Phonebank, Walklist, and Survey, the custom fields do not appear in the Advanced Search screen under the Activities area.

Yet, if you create a custom field set with any other Activity type - e.g. I created a custom activity type of 'my own activity' in the civicrm demo site, the custom fields will appear in the Advanced Search screen under the Activities area.

This is a critical need for surveys, phonebanks, walklist, so that you can search these custom activity fields to find the contacts, and then directly be able to do more actions (register for events, send mailings, etc.) in a much more streamlined workflow.