1. To go https://whsieh.github.io/examples/lorem (or any website with a lot of selectable text).
2. Trigger a long press on some text to start a selection with word granularity.
3. Without ending the touch, pan to more text to extend the selection.
Sometimes, instead of extending the ranged selection to encompass text content near the touch location, this moves the ranged selection to the word under the touch location.
Needs more spelunking to figure out whether this is us or UIKit.