Dude, that sort of transmission is only applicable to the four vedas (and even they exist in rescensions, some have later insertions eg: Maitrayani samhita, and the meter is generally lost due to language shifts). When you say "Vedic" those are the texts which count. Rāmāyana and Mahabhārata are not really "vedic" nor subject to such accurate transmission rules.

So they exist in many rescensions across India each with their own edits and interpolations. Some attempt has been made to create "critical" editions by taking the intersection of existing manuscripts but since there's no expectation of fidelity in transmission, we will never know what the original stories were.

So you can get even the western indologists to agree the battle of 10 kings mentioned in Rigveda very likely happened, and a Vasishtha and a Vishwamitra and a Trasadasyu existed in real life. However the epics leave out or conflict in many details with the aforementioned Vedic texts. Eg: a shantanu finds mention in Rigveda, a Parikshit and Janamejaya are mentioned in later samhitas. However there's no mention of pāndavas, kāuravas or a grand scale war. Neither there is a mention of a vyāsa / krishna dvaipayana in vasishtha's lineage in the accurately transmitted texts. It's very difficult to take Mahābhārata as an accurate historical document.

- you dont know if there was an error that happened when it went via recitation from one generation to the other before it was converged into a book

- my point is that most people fail to consider the fact that there may have been major errors during the entire period of 5000 yrs