CD-RWaste: UDF requires full blanking first?

When formatting a CD-RW onto UDF, unlike normal packet writing, and unlike UDF on DVD-RW, the CD-RW gets a dull blankout first.
What is the purpose of that blanking? CD-R does not require that. Why does CD-RW need it then? It just wastes rewriting cycles.

I am not angry about this restriction, I just wonder, whether it is really necessary.