The viewer crash statistics are derived from a flag integer in the stats packet. That value is deduced by looking for one of a group of marker files that are created and deleted by the viewer as it changes from one state to another. Normally, all of the marker files should be deleted if the viewer exits normally.
At present, the marker files do not distinguish between different viewers or different versions, so a crash in version X may be counted as a crash in version X+Y if the user changes viewers.
For version changes, this is probably not significant, but we know that many users run more than one viewer, so a crash running a Project viewer may be reported as a crash in the Release viewer (since the reporting is done by the next viewer to run).