To catch up any non-Trekkies: “The Chase” was about the Federation racing with the Klingons, the Romulans, and the Cardassians to uncover a mysterious ancient secret on a distant planet. There is a lot of double-dealing and intrigue, but the search will ultimately find representatives from each group beaming down to an uninhabited world and uncovering an ancient holographic message left there eons ago. A member of the Progenitors appears and explains that her species was the very first sentient species in the galaxy. When they had mastered space travel, they were bummed out to find that they were alone. They proceeded to seed millions of worlds with their own DNA, hoping that Progenitor-like species would eventually evolve on each one.
“The Chase” provided a handy sci-fi excuse as to why all the aliens in “Star Trek” looked more or less like humans (one head, two arms, bipedal, walks upright, etc.). While Frakes directed multiple episodes of “Discovery,” he didn’t develop the story for the show’s fifth season, and had no input into the “Chase”-based story. That was the decision of showrunner Michael Paradise. Frakes said very directly:
“It’s just by chance that ‘The Chase’ was my episode. […] In the old days on ‘NextGen,’ you were assigned episodes based on people’s availability. I’m very proud to have been a part of it, though, and very excited that Michelle Paradise chose it as sort of the tipping off point for the season. But it was clearly by happenstance that it happened to be an episode that I had directed then, and now I’m involved with the finale of, so it’s thrilling.”
Paradise could have taken any episode from any Trek series as his jumping-off point, but decided on “The Chase.” As one can see, Frakes was certainly pleased.