The writers of Star Trek: Enterprise created the Temporal Cold War storyline, introducing the mysterious Agent Daniels in the process who was played by Matt Winston in eight episodes. It was a part of the Star Trek Universe that isn't completely understood by many, including Enterprise star, Dominic Keating. And Star Trek: Discovery's revelation that Dr. Kovich (David Cronenberg) had been Agent Daniels all along didn't sit well with the actor either. In fact, Keating considered it a slap in the face.
When interviewed by Treknews.net about his newest podcast with Connor Trinneer, The D-Con Chamber, Keating didn't hold back when asked about the storyline. He said the last part, meaning Daniels, pissed him off and was "a slap in the face." But Keating seemed to be talking more about his character's treatment on Enterprise.
"But if I’m gonna be honest, it kind of used to piss me off that they bring him [Matt Winston] back two or three times a season for really good episodes. And I’d get the ‘Yes sir, no sir, three bags full, sir’ lines."Dominic Keating
To have Agent Daniels referenced at the end of Discovery's five-season run clearly didn't make Keating happy, and to be fair, something he adds later, that some of the Enterprise characters were underused is correct. There was never enough of Travis Mayweather (Anthony Montgomery) or Ensign Hoshi (Linda Parks), either. Occasionally, Dr. Phlox (John Billingsley) would get a good episode, but the other characters were rarely center stage. For the most part, Enterprise revolved around Captain Archer (Scott Bakula), T'Pol (Jolene Blalock), and Trip Tucker (Connor Trinneer), much like Star Trek: The Original Series centered around Captain Kirk (William Shatner), Mr. Spock (Leonard Nimoy), and Bones (DeForest Kelley).
Overall, though, the entirety of Enterprise has been overlooked, and maybe this was the Discovery writers way of bringing in a small piece of the series as a nod. But it wasn't an effort that left a good impression with Keating.