I think the issue for some (including myself) is that this revelation shows that the vulnerability of a compromised document is greater than the apparent contents of the document. It includes all keystrokes, which could expose other ideas the writer might have had (but discarded), etc. This fact makes me even less inclined to use Google docs.
The parent comment was clearly aware of the versioning feature, and appears to be more surprised by the keypress-level granularity of the versioning that may not have been apparent in the official UI.
