UCT (Re: pgsql: Update time zone data files to tzdata release 2019a.)

Re: Tom Lane 2019-04-26 <E1hK8qL-0005yH-VX@gemulon.postgresql.org>
> Update time zone data files to tzdata release 2019a.
> 
> DST law changes in Palestine and Metlakatla.
> Historical corrections for Israel.
> 
> Etc/UCT is now a backward-compatibility link to Etc/UTC, instead
> of being a separate zone that generates the abbreviation "UCT",
> which nowadays is typically a typo.  Postgres will still accept
> "UCT" as an input zone name, but it won't output it.

There is something wrong here. On Debian Buster/unstable, using
system tzdata (2019a-1), if /etc/timezone is "Etc/UTC":

11.3's initdb adds timezone = 'UCT' to postgresql.conf
12beta1's initdb add timezone = 'Etc/UCT' to postgresql.conf

Is that expected behavior? Docker users are complaining that "UCT"
messes up their testsuites. https://github.com/docker-library/postgres/issues/577

Christoph