Try this:
Some normal text
Label One:: This will demonstrate
Label Two:: the difference to the number list
Some text in-between.
. One
. Two
. Three
+
====
This is a block like suggested by Dan in https://github.com/asciidoctor/asciidoctor/issues/520
====
. Four
+
--
An open block can be an anonymous container,
or it can masquerade as any other block.
(found in http://asciidoctor.org/docs/asciidoc-syntax-quick-reference/#more-delimited-blocks)
--
. *Fifth is bold* +
Some text
So, I would suggest to do it like in the fourth point. That's almost like suggested in the link, but using an "open" block with "--". This is not set off like a normal block with "====".
I also tried to number a labeled list automatically, but it did not work. To be honest, I also do not know if this would be easily solvable (I think this would be a new feature), and therefore quite a lot of work for such a rare use case.