I just came across this and found it fascinating. This really is a must-watch for DIY guitar builders and woodworkers in general. Audio quality isn't the best I'm afraid, the vocals are a bit muffled, but my tired old ears could still make it out.



Main results are
1) End grain-to-end grain glue joints are the strongest type of joint
2) The glue is not always stronger than the wood - it all depends on the grain direction at the joint.

Lots of 'but what if...' questions you can ask, so it's not fully a comprehensive result. The tests were all done with the wood under compression. No tests under tension (pulling the joint apart from the ends), or shear (twisting the joint). I wouldn't expect the results to be significantly different with regards to the glue strength, but the wood strength figures could change a bit.