Subsidiary restriction on custom field with record type ACCOUNT is not working

I set subsidiary restriction on a custom field with record type ACCOUNT , but it is not working. When I make default access level as none, and gave edit access to a particular subsidiary, none of the subsidiaries are able to see the field.

If i make the default access to edit, and restrict edit access to a particular subsidiary, every single subsidiary is able to edit it.

I want just one subsidiary to be able to edit that field and all other aubsidiaries should not be able to even view that custom field.

Appreciate any suggestions as to how to tackle this issue.