The file /usr/share/zoneinfo/zone1970.tab contains a corrupted row that
tags Asia/Tokyo with both the JP and AU country codes:

JP,AU +353916+1394441 Asia/Tokyo Eyre Bird Observatory

The coordinates (+35°39'16", +139°44'41") point to Tokyo, Japan — not
to the Eyre Bird Observatory, which is located in Western Australia
(approximately -32°15', +126°18'). It looks like two separate rows
were merged: the real Tokyo entry (JP, Asia/Tokyo) and a missing
Australian entry for Eyre Bird Observatory (probably AU,
Australia/Eucla).

The user-visible effect: TZInfo::Country.get("AU").zone_identifiers in
Ruby (and equivalent calls in other tz libraries) now lists Asia/Tokyo
as an Australian zone. Application code that enumerates "all
timezones in Australia" gets Tokyo, Osaka, and Sapporo mixed in.

Reproducer:

$ grep -E '^(AU|[^[:space:]]+,AU)' /usr/share/zoneinfo/zone1970.tab

... shows the JP,AU Asia/Tokyo row at the bottom.

Expected: Asia/Tokyo should be tagged with JP only. A separate row
should exist for the AU entry (likely Australia/Eucla).

Hi,

I think this is actually correct. zone1970.tab group zones so that each
row stands for a timezone where civil timestamps have agreed since 1970.
It means that both Tokyo and the Eyre Bird Observatory got the same time
since 1970.

This is also correct. In case multiple countries are covered by the same
row, the most populous city is used, and that country is listed first.

See the header of that file for more details.

This should probably use zone.tab instead, which does not try to group
timezones.  Indeed there are two distinct entries there:

AU      -3143+12852     Australia/Eucla Western Australia (Eucla)
...
JP      +353916+1394441 Asia/Tokyo

Regards
Aurelien