I think the ability to double click on the artboard to create a text box as a child of the element you are clicking in is intentional. So I assume it was intended as a feature and therefore is not a bug.
I have been accidentally double clicking and creating text boxes when I try to select boxes that aren't easily visible or are small. Or when I try to click into a text box to edit the text but I miss the box. Maybe I'll eventually learn not to do it.
I'm not creating a lot of text boxes quickly but maybe someone else would be. Is that the reasoning behind making it so easy to create a text box?