Is it advisable to use non-scientific method to teach science courses?
"What if..." Is the bread and butter of science and mathematics. Making outrageous guesses and then checking them is part of the toolkit for professional thinkers. 

In your examples, you say that the author takes the stance that one event only potentially explains another, which seems fine from a scientific point of view.

As others have said, when you popularize you often intentionally leave out some subtlety. This is really a function of your intended audience. I leave out some subtlety when I teach intro calculus.

As to whether or not the author you reference does this badly or irresponsibly, I can't form an opinion without reading what they wrote.