Looking at the spec, the change-info provides an author, time and optional comment related to the change. Lining this up visually with the start and endpoints seems simple enough.
The primary benefit of this approach is that documents with change tracking active will actually display sensibly in WebODDF... and editing from WebODF will export nicely into other suites.
This isn't a high priority item for me, more a technical musing about whether it was specifically considered and avoided :)