I admit I am a bit surprised by the strength he got in end grain joints but I do not believe it is at all meaningful. We know that wood expands primarily across the grain, not along the grain. If we glue end grain to side grain, the expansion and contraction of the end grain portion will destroy the joint over time. So thinking woodworkers do not do this. End grain to end grain joints could move in unison but I suspect they would not. I don't think the movement is uniform across the growth rings so I suspect humidity changes would destroy this joint too. But it would be interesting to see a test.
Side grain to side grain did not fail at the joint, they failed in the wood. As we know wood is weaker in this direction.
In short, we glue up the way we do because we are allowing for the movement of our projects across the grain. It's not that gluing to end grain has no strength. It's that humidity changes will destroy joints between end grain and side grain.
Would trim suppliers bother to finger joint pieces if simple but joints in end grain were dependable? Wastes wood, requires more cutters and glue. I think it is obvious they would not waste their money if end grain joints are dependable.
The only new information in this is that at least initially, end grain joints are stronger than wood is across the grain. Doesn't mean that will continue to be true as humidity changes. Even if it remains true, I do not see how we can make use of that information.
