Does the status of a female slave (Umm Walad) regarding manumission upon the master's death depend on her faith or moral conduct?

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Manumission upon the master's death applies equally to a Muslim or a non-Muslim, and to a chaste or a dissolute woman. This ruling is held by the Imams of jurisprudence in the major cities because the prerequisites for manumission, such as tadbir (pre-arranged manumission) and kitaba (contractual manumission), are the same for Muslims and non-Muslims, and the chaste and the dissolute. The rationale is that her manumission stems from the mixing of her blood with his and her flesh with his flesh; thus, if they are equal in lineage, they are equal in the resulting legal ruling. However, a contrasting report from 'Abd al-Malik ibn 'Umayr regarding 'Umar ibn al-Khattab states that if the Umm Walad converts to Islam, remains chaste, and adheres to piety, she is manumitted; but if she apostatizes, engages in immorality, and betrays trust, she reverts to servitude. Furthermore, concerning the Umm Walad of a man who apostatized, 'Umar ibn 'Abd al-'Aziz ruled that she should be sold so that someone of her religion might take her captive. Based on 'Umar's reported conditional statement, it is more appropriate that manumission should be restricted to the chaste Muslim woman, excluding the dissolute non-believer, due to the lack of definitive proof supporting the manumission of the latter.