I'm just wondering what I might be missing regarding collecting the gem from Hang 'em High's level 7 entrance. Once I reach the end of the level, I can slide double jump over to the platform that moves you back to the boardwalk, but the camera doesn't pan over and I'm unable to collect the gem. Is there a specific action or trick that I'm missing to do this properly?

The difficulty with learning yellow gem skip is the fact that it is a blind trick done offscreen, making trying to learn the skip through watching a video really difficult.

So to start with, setting up the jump:

Make sure you are lined up on the last plank, near the crack in the last plank, on the pathway you start the jump from. this is where i like to set up for the jump and I have no problems with it. Also, make sure you face the warp when you attempt the jump. If you do not face the warp when attempting the jump, and face the camera, the camera then adjusts further back to account for the game thinking you are going to walk backwards. This messes up the location of the camera, and will probably make the glitch not work. It makes the skip very inconsistant for me at least.

the jump:

You need to perform a Neutral slide jump into a double glitch high jump to cover the distance. Not much more explanation is needed here, this isn't hard.

Landing on the platform:

You need to land on the platform neutrally, that means with no directional inputs the frame you touch the platform onwards. This means you need to let go of holding left before you land on the platform. But the hard part is making sure you dont let go too early and fail the jump. the sweet spot is letting go right after the end of the spin in the double glitch high jump used to cross.

Glitching the camera:

Tapping up then down. simple. crash essentially turns around without moving but does his walking animation. i suppose if you want a visual of how short/long this tapping is.

note: after getting the glitch, if you stand there without moving on the platform then it will go back to the main level camera at the end of the platforms journey. avoid this by holding left on the platform and 'locking' the newly glitched camera.

If you failed to glitch the camera it is most likely because you failed to land neutrally, in some cases failing to tap or having a bad camera at the start. 
I hope I thoroughly explained everything you need to know. There is a lot to this trick that can't be learned by watching the videos of the skip since it is done off camera, and I hope this helps people pick up and understand everything behind yellow gem skip.

Levante, I actually made a video about a month or 2 ago to set it up easier, its on YouTube! Ill share the link with you!
https://www.youtube.com/watch?v=j-spn9B-o5c
Hope this helps!

Wow. I've never seen that one before. Awesome. This game truly sucks.

Interesting! So that means you can get the yellow gem without having to get 10 relics and going to Hang 'Em High's Death Route via Secret Warp Room - just slide jump, double jump, Death Tornado Spin, and then glitch the camera.

I learn something new about these games every day.