When you add a dash to your first test it becomes a parent checkbox lines below with dashes with indent are child checkbox.
When you have no dash at your first test line it’s just a text. So it’s not a parent checkbox. Lines below are still child checkboxes but they have no parent. So it’s checkbox behavior are not work.
It could be a code block because of indentation (4 spaces or tab) but it needs an empty line before the content.
The only point here what it’s not a problem with an app. That’s a default Markdown behavior and developers can’t do anything with it (only if they can change Markdown specs somehow).