I don't think that really applies. The "purpose" is being a Linux distro. If it is changed to being 100% based off debian, it is still serving that purpose, but it would empirically false to call it a Ubuntu-based distro.
Originally Posted by dee.
I think a better analogy would be if you take a shovel of brand A, then replace the handle, shaft, and head with those made by brand B, would it still be a brand A shovel? At what point does it cease being a brand A shovel and start being a brand B shovel?