I can watch YouTube videos of it being tested and see it’s true, so I don’t doubt it’s true. I fully believe it’s true, I just can’t grasp why.

In every single test I see the wood on the mortise side rips apart before the glue. If the loose tenon pulled out I’d understand it, but that isn’t happening. If the glue failed, again, I’d understand it. I understand that the tenon side is going to be extremely strong, but again, even in a loose tenon that’s not the failure point.

For what reason is a loose tenon like a Domino weaker if it’s the wood itself that fails?