Because the chord has ^2 and ^6 and because this is a tritone interval it would normally resolve to to ^3 and ^5 pointing to III as tonic. But in minor we overide this function and because of the 5th relationship with the dominant chord, the ii chord becomes a predominant chord. So does this mean that ii°/iim7b5 has two functions in minor keys or instead, should we say that if the chord resolves and the tritone interval is allowed to resolve to III then effectively we can no longer label the chord as ii°/iim7b5 but must call it a vii°/III since it is not functioning here as a subdominant chord but as a secondary dominant chord moving to the relative major key.
