It is desirable to have only a "Blank" value for certain dimension combinations in the account structures.

In AX2012, you can click on "Allow Blanks" and have only "Blank" as the available combination.

In D365, when you click on Allow Blanks, the system inserts a wildcard (*) which allows any other value as well. In other words, you cannot just have "Blank" as a financial dimesnion value.