Nothing has suddenly changed in the world of joinery for me. Except perhaps for my understanding of why things are the way we have all observed them to be.
The point that the research seems to make is that glue is not in fact stronger than wood. Glue is stronger than lignin and wood fibers are stronger than glue. Good joinery takes advantage of this fact by having wood fiber cross the joint.
In the scaffold example, I would not trust a 2x10 beam that was end glued either, but neither would I trust a continuous beam whose grain ran perpendicularly. A lap joint is stronger in this application because wood fibers cross the joint. But if I were making a lap joint maybe it would be worthwhile to put glue on the end grain as well as the long grain. You could make up an end glued beam that was strong enough, but it would need a huge cross section, and nobody is going to design a beam that uses that much wood. Wood fibers aren't just stronger than glue, they are a lot stronger.
A simple 45 degree miter will fail due to wood movement. If the wood swells or shrinks it changes the miter angle.