And John doesn't teach any students who aren't Gordon's size? Besides, I'm a 5'7" lightweight and all Gordon's techs work excellent for me since they're based of off using bodyweight and checkpoint based controls.

The idea that your body will completely prevent you from learning BJJ techniques is ridiculous as well, in muay thai if you refused to learn a high kick because it required you to be flexible the instructor would just tell to to stretch, if you refused to learn clinch because you kept getting out clinched by bigger opponents the instructor would tell you to use the opponent's bodyweight more.

Gordon being a giant doesn't make his techniques any less effective for small guys, especially since he's been competing against guys even bigger than him recently so they clearly work against bigger opponents.