Video timestamps don't align up correctly

[Wumpf]

Both with native & web Chrome this video is always a little bit off in its backed-in and reported timestamps

bunny_timestamped_h264_1080p_10s.mp4

This was generated using:
ffmpeg -i Big_Buck_Bunny_1080_10s_1MB_h264.mp4 -vf drawtext="fontsize=30:rate=60:fontsize=72:text='%{frame_num} %{pts}':fontcolor='white':boxcolor=0x000000AA:box=1:x=860-text_w/2:y=960" timestamped.mp4

The problem is likely not limited to h264, but it may be until proven otherwise.