I played around with this on the demo page and found that while the generated "TLDR" are pretty good, they tend to generate sentences composed of fragments of existing sentences. Basically, it seems vaguely extractive in nature. Never did I see it summarize a concept in new words, or try to dumb down a complicated concept further than the original paper did. Given the results of GPT3 I would think that it should be possible to do much better by now, at least with enough data and compute time.