There is a lot to say, so I will try to make this as short as possible.
Games on ESPN+ don't have the same production values as those of other ESPN/ABC games, meaning there are no pylon cameras and no cameras stationed to shoot down the sidelines. They don't necessarily have access to the cameras the scoreboard uses, only what ESPN cameras show. If they are lucky, they may have a cart camera on the goal line. If the RO doesn't have a clear shot down the line, he/she has no choice but to go with the call on the field. Should the R/O have gone through the motions and reviewed it? I would have, even though I had no shot. Call it a PR review if you want, but they are trying to shorten the game and eliminate PR reviews altogether. You can compare it to a first-down spot. If the camera isn't exactly on the line-to-gain, it's hard to determine the spot. The goal line is the same.
What he/she probably did was tell the R he didn't have a shot, the R probably told Dykes that even if he challenged, he wouldn't win and would lose his challenge. Dykes did the right thing and saved his challenge for a play that might come up later. The R did Dykes a favor.
It's entirely possible the RO was told by the ACC's video center not to review, as well.