People reveal their assumptions through the explanations they never think to offer.

What gets skipped is more informative than what gets said. Somebody explaining a plan will spell out the parts they consider debatable and glide silently over everything they take as obvious, which means the silences map their model of the world precisely. Nobody does this deliberately. It is simply impossible to notice the ground you are standing on while you are pointing at the view.

Listen for the unexplained step in the next thing somebody tells you, and ask about it plainly. Then try it on yourself: write down what you would not bother explaining, and see what you have been assuming.