As Goldstar said, this isn't the argument that's being made here. The only hints the show ever gave pointed squarely at Dick Grayson being under Robin's mask. That is not in dispute. The argument being advanced is that it doesn't matter that it's Dick Grayson under the Robin mask. To flip this around, let me pose a different question to you: were there any moments in the show where Robin's secret identity was truly significant? Some plot point where his identity as Dick Grayson was the lynchpin of a plot point (vs. being Jason Todd or Tim Drake)? I'm not talking about Larry's name being Dick Grayson spelled backwards; Larry is the same character whether his name is Kcid Nosyarg or Nosaj Ddot or Susan. I'm not even talking about the moment when he tells Slade with barely sublimated anger that he already has a father while bats flit around in the background, because all the Robins could make that same assertion. We are arguing that there isn't any such moment anywhere in the Teen Titans series. Raven's identity as the daughter of Trigon is important since most of the Trigon story arc hinges on that background. Beast Boy's identity is tangentially important in the episodes where the Doom Patrol showed up. Starfire's identity as Koriand'r of the Tamaranians was important because of the way it affected her relationship with Blackfire and in that episode where she had to go get married. Robin is roughly equivalent to Cyborg. Other than the origin story episode, I can think of no moments in the show where a plot point mattered that it's Vic Stone, former football star, under all those mechanical implants. It doesn't matter that it's Dick Grayson under the mask. Attempting to swing back on topic, I think the attitude of the show with regards to Robin (and Cyborg) are related to understanding why it's not important who Red X "really" was when it wasn't Robin, and why it's not really important to know if that was "really" Terra in the last episode of the show.