Greetings,

Step to reproduce:
1- Enable (org-indent-mode) in an org buffer.
2- Use the command (org-inlinetask-insert-task)
3- Insert some text between the task's title and the keyword END
4- Notice that the text between the title and the keyword END isn't
properly indented.

I'm not sure if this is helpful, but I noticed that we have the right
indentation when using the code from org-inlinetask.el of this old
repository:
https://github.com/ngz/org-mode-lists/blob/master/lisp/org-inlinetask.el

Thanks for your work, org-mode is an amazing piece of software.