Is Dhamma one or many? It is one. In other words, the world is a particular way and it is only that way. Therefore, either someone will have a correct understanding of Dhamma or they won’t. In the event that they have the correct understanding, they will be on the noble path and eventually attain Nibbana. If they don’t have an accurate understanding of Dhamma, it will not be possible for them to attain Nibbana (you can’t solve a problem if you don’t understand what the problem is).
As such, I can’t help but feel that discussions about specific traditions, lineages and teachers often miss this critical point. So as pedantic as this may sound, if a tradition or teacher claims their tradition or teachings can lead to Nibbana, strictly speaking, they are wrong – only an accurate understanding of Dhamma does that.
This isn’t to suggest that there will be no traditions with practitioners who are ariyas, rather, if they are, it’s because they’ve comprehended Dhamma.