Custom Fields limited to Custom record subtypes are not available to batch update via profile

I have confirmed this bug in 3.1.5 and 3.1.6, but not tried in 3.2, or any previous versions, however there is reason to believe that this bug did not exist in 2.x.

If you create a custom record subtype, like a subtype of contribution (call it test fee), and then create a custom field group of fields that only apply to that subtype, these fields will not be available for editing via batch update with profile even though you can add them to a profile and a column will be displayed, the column will be empty.

This bug prevents the use of batch update via profile with any custom field that is limited to a record subtype, vastly constricting the utility both of batch update via profile AND using subtypes and custom fields limited to them.