Convert list to subtree without eating newline before next tree item

Question

Say we have this file:

* A
  - L1
  - L2
* B

If we execute org-list-make-subtree on any position within the list (the two lines with L1/L2), we get

* A
** L1
** L2* B

So the conversion "eats" the newline after the last list item.

When having an additional newline before, it still eats the newline:

* A
  - L1
  - L2

* B

After conversion:

* A
** L1
** L2
* B

It happens at any level in a tree, and no matter whether the list is indented or has further levels.

Whether you always use a newline before a new heading or not - I don't see a reason for this behaviour to be useful because you manually have to add the newline to restore your previous layout.

Why is that so and how can it be prevented? Should it be filed as a bug?

Emacs version: 26.1 (with Spacemacs 0.200.13.x)