You talk about "rebasing" changes in the article. Does that not imply a "transformation" step?
Unlike traditional Operational Transformation, though, there are no "transformation properties" [2] that this rebasing needs to satisfy. (Normally a central-server OT would need to satisfy TP1, or else users may end up in inconsistent states.) Instead, the rebased operations just need to "make sense" to users, i.e., be a reasonable way to apply your original edit to a slightly-further-ahead state. ProseMirror has this sort of rebasing built in, via its step mappings, which lets the collaboration-specific parts of the algorithm look very simple - perhaps deceptively so.
[1] https://prosemirror.net/docs/guide/#collab [2] https://en.wikipedia.org/wiki/Operational_transformation#Tra...