timestamp bogus parser?

Hello,

I tried:

psql> SELECT TIMESTAMP '2020-12-23Z19:28:45';

The result of which is:

2020-12-23 00:00:00

This is disappointing. Ok, my fault, I should have written TIMESTAMPTZ, or
use T instead of Z, or whatever.

Anyway, is there a rational for this behavior? I would have expected
either the time to be taken into account or an error message, but
certainly not half of my string being silently ignored. Skimming through
the doc (Section 8.5.1.3) did not provide an answer.

Any clues? Is this a bug?

--
Fabien.