What is the primary evidence for establishing menstruation based on distinguishing features (Tamyeez) in cases of Istihada?

Primary text

The evidence for prioritizing distinguishing features over mere habit is the narration of Aisha regarding Fatimah bint Abi Hubaysh, who complained of continuous non-purifying flow. The Prophet (peace be upon him) instructed her that the flow indicating menstruation is dark and recognizable, and she should cease prayer during that time. When the flow changes, she should wash away the blood and pray, as the remaining discharge is merely from a vein (Istihada). This hadith is one of the three foundational reports upon which the ruling of menstruation rotates. Ibn Abbas corroborates this, stating that the blood other than the true menstrual blood will appear like water used for washing meat after her customary days have passed.