Clearing a precinct is not the issue. It is recounting only one precinct of a multi-precinct memory card and then uploading that is the hard part. AccuVotes upload their results all or nothing. This is also the case with VTS upload.
It begs the question though, why did VTS allow clear by precinct? Under what circumstances did VTS customers clear one precinct of a multi-precinct vcenter? I suspect this "feature" was just a hold-over from before VTS and the AV knew about multi-precinct vcenters.