Huh, I thought it was from the episode after Shotaro used HeatTrigger's Twin Maximum and messed up his body. As for the dialog; I thought it was something more like this;
W: We're going to do a Rider Twin Maximum
Accel: That's a thing?
W: Yep
*edit
I just remembered what the Invisible arc is (although calling it an arc when it's only two episodes long doesn't really seem right to me) and that the Twin Maximum stuff happened during it
I think you might have watched a different translation than I did. Even assuming that two translators are equally skilled, it's not an exact science. Even when reading up on trivia for this show I've seen multiple different versions of things as simple as main characters' catchphrases ("Despair awaits you at the finish line" vs "Your goal is despair" for one example). At least three different groups have fansubbed W and they're likely to all take certain liberties and different interpretations when it comes to keeping the personality and tone of the original dialogue across such a huge language/culture barrier. I honestly couldn't say which version of that exchange is better translated, but I do know that I captured the GIF straight from the MP4 I downloaded. Either way, it's likely that your memory is spot-on.
I guess that is a weird term. I'd call them two-parters, but usually when I hear that I think of two-part specials, and the final episode was the only one that
wasn't a two-part set, so that feels weird to me too. It was a really fun gimmick for me, though.