If buffer sorting is disabled, when saving a session using the Sessions plugin the manual buffer order set by the user gets lost, and on reopen the buffers are in what amounts to random order.
This patch is a slightly improved version of the latest patch submitted to ticket 165.
So once jEdit 5.3pre1 comes out, Sessions will behave correctly without the patch, and this is only for getting Sessions to work properly with jEdit 5.1 and 5.2 ?
If I've understood correctly what is included in which versions of jEdit, yes. Patch #548 on jEdit should make this patch unnecessary.