Hi 
Mesh indices are not updated/removed when using Mesh.convertToUnIndexedMesh().
despite the description;
This method removes all the mesh indices and add new vertices (duplication) …
manually calling Mesh.updateIndices() returns the expected result.
Hey!
They are removed from the GPU. The local CPU copy is not delete because you may want it later (And we are not bad guys deleting your data ;))
Ahh, makes sense.
I used indices.length to check if unindexed or not, so it confused me a bit 
Chaining a updateIndices() is not a big deal 