Name for Turning DAG into redundant tree
I am not aware of any standard name for that kind of tree.  One of the wonderful things about language is that we can describe things we don't already have a name for; there are many more interesting concepts than there are pre-existing widely-recognized names.  I recommend that, if you find in your writing you need a concise name for it, you choose a name that seems suitable to you, and define it before first use.