That's pretty much the definition of "rebase" and again, that's a functionality of the algorithm on top of the data structure (Proof of Work) not the data structure. The raw data structure is still a merkle tree even if in practice the algorithm suggests to people there is only one rebased trunk. But even that isn't entirely true in practice because there are still multiple rebased "branches" among the Bitcoin forks such as Bitcoin Classic, Bitcoin Gold, etc. All of those are branches that share the same conceptual merkle tree. Even if they aren't "Bitcoin" that's more of an algorithmic and political distinction at that point, not a technical one by means of data structure. It's not the data structure that makes it a chain, it's the algorithm and the politics, hence why I think blockchain is a misnomer for the data structure itself.