cccombiner passes through timestamps but not segment

This pipeline gets prerolled but doesn't stream:
gst-launch-1.0 -v videotestsrc ! x264enc ! cccombiner ! fakesink sync=1

The following pipeline shows the preroll buffer is at 1000 hours running time:
gst-launch-1.0 -v videotestsrc ! x264enc ! cccombiner ! identity single-segment=1 silent=0 ! identity silent=0 ! fakesink sync=1

Fiddling with the start-time* properties doesn't seem to affect the segment produced.