There is indeed no apparent reason to do that, but I assume developers got used to the process I described above when maintaining upstream packages and bump the maemo-specific version number when packaging.

Another possibility is that internal processes involve separate roles of coder and packager. 1.2.40 is the version of the code and 8 is just a number that increases each time a new package is made public. This way, small changes done by the packager do not interfere with the bugfixes of the coder, and no coordination is needed between them regarding the version numbering.

A third possibility is that the same codebase is shared between symbian and harmattan and so my previous post applies verbatim.