When I run below command on a video file:

ffprobe -show_frames test.mp4
I got below output (1 frame copy)
[FRAME]
media_type=video
stream_index=0
key_frame=0
pkt_pts=897000
pkt_pts_time=9.966667
pkt_dts=897000
pkt_dts_time=9.966667
best_effort_timestamp=897000
best_effort_timestamp_time=9.966667
pkt_duration=3000
pkt_duration_time=0.033333
pkt_pos=162930
pkt_size=624
width=640
height=480
pix_fmt=yuv420p
sample_aspect_ratio=1:1
pict_type=P
coded_picture_number=299
display_picture_number=0
interlaced_frame=0
top_field_first=0
repeat_pict=0
color_range=tv
color_space=unknown
color_primaries=bt470bg
color_transfer=unknown
chroma_location=left
[/FRAME]
How to understand below fields:

color_range=tv
color_space=unknown
color_primaries=bt470bg
color_transfer=unknown
chroma_location=left
I am thinking about why two color field is unknown but only the color_primaries field is bt470bg?
what's the relationship between bt470bg and BT.601 or BT.709?

Is this a valid file? (I guess it should be tagged fully or not tagged at all)