ReWriteable DVD is called RW, but BD-RE?
Why not CD/DVD-RE and BD-RW?
Maybe Sony would know
RE is short for Recordable and Erasable. This is predefined in specs.
IIRC CD-RW was once named CD-E which stands for CD Erasable. But later changed its name to CD-ReWritable…
It is actually both.
They support direct overwriting, as far as known to me.