In the manumission and divorce examples, the legal relationship is not symmetrical. The text contrasts a statement of freedom addressed to a wife with an intention of divorce and a statement of divorce addressed to an enslaved person with the intention of manumission.
«حررتك»
I have freed you.
«طلقتك»
I have divorced you.
In the specific historical Hanafi illustration, the former expression with an intention of divorce is considered effective, whereas the latter with an intention of manumission is not. Manumission concerns removal of ownership of an enslaved person; divorce dissolves a marital entitlement. Their legal causes and effects cannot simply be equated.