I'm very surprised to see the Polyurethane construction adhesive perform so well.

I noticed it blobbed over both ends. I wonder if the entire blob was helping redirect the load from tension into compression onto the ends. And/or it did a better job resisting the bending moment induced by his asymmetric setup.

I'm also not convinced that the other adhesives compromised the PETG. PETG, while not as resistant as Polypropylene, High density Polyethylenes, or Fluorinated plastics, it's still pretty darned resistant.

At the temperature he was testing at I would expect PETG to survive most acids, bases, and other solvents for days.

Maybe some of the glues were too rigid and robbed the PETG of its strength by preventing flexing?

MMA being at the top makes sense as it's a true chemical weld at that point.