> only ~100ms for each interaction

Wow.

I want to stress this isn't something I measured. There are just these noticeable lags before the sigmoidal animation starts when, e.g. opening a folder.

It's on top of the latency inherent to the animations of sliding, wiggling, wobbling, jiggling, etc. that are throughout the interface. ~100ms on top of a ~600ms input-blocking sigmoid probably just looks like a 700ms sigmoid to people.