It's possible to modify a document without getting a new entry in the history

When history is enabled of course.

You end up with the version properly set in the document table and rcs table but the actual history is not updated which mean among other things that you don't see your version version in the history view but the content is definitely changed.

How to:

document.setContentDirty(false);
document.setMetaDataDirty(false);
xwiki.saveDocument(document);

We could say that it's a feature but the UI does not seems to be aware of such a feature...