I would like to know how wetting the end grain prior to glueing [common practice to increase bonding] would have changed the outcome.
And surely it is the end grain exposure in the mitered joint which makes it so strong. Letting the glue penetrate more deeply should make it even stronger.
Dovetails would have done better if there had been as many pin/tail pairs as the box joint — similarly, extending this, a blind dovetail should have done much better — but I would be concerned about how glue alone on endgrain would hold up over repetitive stress.
The Woodgears folks did a rather different test which is interesting:
as did Fine Woodworking:
Hi @WillAdams ! Good to see you hanging out. Thanks for the additional information. Hope all is well with you.