The Mekhilta raises an objection to equating the tam (first-time gorer) with the mued (habitual gorer). The two categories are not truly parallel. A mued's owner pays kofer — a ransom payment to the victim's family. A tam's owner does not. Since the legal consequences differ, perhaps the rule equating all forms of killing with goring should apply only to the mued and not the tam.
The Torah resolves this with the phrase in (Exodus 21:29): "it killed a man or a woman." This language appears redundant — we already know that killing a person triggers legal consequences. The Mekhilta explains that the phrase is "extra," included specifically for the purpose of creating a gezeirah shavah — a verbal analogy.
The same phrase "a man or a woman" appears in (Exodus 21:28), regarding the tam. By using identical language in both the tam and mued passages, the Torah creates a bridge between them. Just as the mued rule covers all forms of killing (not just goring), so the tam rule covers all forms of killing.
The objection was valid — the two categories do differ in their financial consequences. But the Torah anticipated the objection and preemptively linked the two passages through shared language. The verbal bridge overrides the logical distinction. Even where the legal frameworks differ in their details, the fundamental principle that all animal-inflicted deaths are treated alike applies to both categories equally.