More frame counting mysteries H.264 -> multifilesink

[pisymbol .]

Pipeline snippet:

matroskamux name=muxer streamable=true ! multifilesink name=mfsink
post-messages=true next-file=5 max-file-duration=\"{}\" location=\"{}\"
... ! video/x-h264, stream-format=(string)byte-stream ! h264parse !
identity name=tap0 ! queue ! muxer.video_1

Why do I see more buffers under tap0's handoff than what's written into the
MKV stream on disk?

It seems to happy right until the first 60s file is rolled over where I see
X number of frames seen by tap0 but only <X frames written to the MKV file.

-aps
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