There's a lot to like in this article, but I don't quite agree with the setup. I think it's better to think of "contrastive" approaches as being orthogonal to basic self-supervised learning methods - they represent an additional piece you can add to your loss function that results in very significant improvements. This approach can be combined with existing self-supervised pretext tasks.
BTW, one thing which makes it a bit hard to get into self-supervised learning is that the most common benchmarking task involves pretraining on Imagenet, which is too slow and expensive for development.
I recently created a little dataset that is specifically designed to allow for testing out self-supervised techniques, called Image网 ("Imagewang"). I'd love to see some folks try it out, and submit strong baselines to the leaderboard: https://github.com/fastai/imagenette#image%E7%BD%91
I've discussed these ideas here, for those that are interested in learning more: https://www.fast.ai/2020/01/13/self_supervised/