Sound like this is the result of 1.17.2 adding support for the H export option. That option controls the level below which headlines are converted into list items. The Emacs default for this option is 3, so the org-reader, aiming for maximal compatibility, does the same. This therefor is indeed indented behavior. However, two similar questions came up on pandoc-discuss already, so I'm starting to wonder if that was an error. It seems unexpected to many people and maybe pandoc should use a different default value.
somewhere near the top of your org-mode file. See the orgmode documentation for details. Of the export options listed there, pandoc v1.17.2 and up supports ^, ', *, -, arch, author, creator, d, email, and H. The current master also supports the todo option.
@tarleb thanks for this workaround, I'll try that.
I can see that you are right and default exports are behaving same way. I hit the problem when I tried export to textile which is clearly broken and can't work with this. It renders html instead of textile when it find this list instead of heading. I should report it to different issue probably.
Anyway one thing is sure. It is problem because it behaved differently for long time and now there is confusion from it. It would be great to at least let users now somehow.