The goal is to replace a block with another block, say "new"replaces "old". But it should also replace all blocks with the name "old" inside other blocks. And in the end all replaced blocks should have the name "new".
With -INSERT old=new all replaced blocks are named "old", not "new".
I cannot rename "old" to "new" because I might rename blocks with the name "new" which existed before the insert. I tried to use a temporarily name before the insert ("old" > "temp"), but this doesn't work also because afterwards I want to rename "temp" to "new" which is not allowed when "new"already existed in the drawing.