Now when checking for shortening of leaf tuple is added LongValuesOK become slightly redundant. I'd propose to replace it with more legible name as LongValuesOK doesn't mean they are warranted to be ok just that we can try to shorten them? What about tryShortening, trySuffixing or can(Try)ShortenTuple?
Or maybe it's even more logical now to invert it and make dontTrySuffixing for use in the opclasses for kd-tree, quadtree etc which are warranted to have the same key data length at any tree level ?