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.