Omg, I was not a BERT coauthor! But thank you so much for writing this, I had no idea that other post could have accidentally implied this. I will revise that section.
I use Sketch to export SVGs, and animate them with anime.js. Here's an example of some illustrations where I did this [1]. It's not without issues though; using external (i.e., not inlined) SVGs is surprisingly tricky, and you quickly run into edge cases with groups and transforms---some notes here [2].
I like this approach because it decouples drawing and animating, and with SVG it is resolution and bandwidth-friendly. I was already used to making figures for research papers with Sketch, so I just suck with that, and added anime.js on top. However, for more complex motion like you might be hinting with your post, I could imagine a GUI tool with a proper timeline and tweening to be more ergonomic.