Hi ya'll, i kept working on this project and found an acceptable way to do this.
I began examining the issue and found that the more I experimented with pinning in GSAP, the more it seemed like I was hacking together a makeshift solution rather than using it as intended. Eventually, I re-discovered that CSS's position sticky property essentially provides the functionality I was after. I combined that with GSAP's draggable plugin (along w some smooth scrolling) and I was able to come up with this:
https://codepen.io/xyeres/pen/poxWeqE
I'm open to constructive criticism if you spot something you think could be improved!
One thing I'm wanting to do but can't figure out is making the draggable instance scrollable when the user hovers and scrolls, is that possible with draggable? (right now if you scroll the page, the timeline moves, but i was thinking of having the timeline move independently of the rest of the page at a faster rate to allow the user to navigate the timeline separately from the page position, like you can when you drag left and right)