BUG #17513: recompressing already-compressed data via VACUUM FULL or CLUSTER does not work

The following bug has been logged on the website:

Bug reference: 17513
Logged by: Kiriakos Georgiou
Email address: kg(dot)postgresql(at)olympiakos(dot)com
PostgreSQL version: 14.3
Operating system: Linux
Description:

Per
https://www.postgresql.org/message-id/E1lNKw9-0008DT-1L%40gemulon.postgresql.org
and https://www.enterprisedb.com/blog/configurable-lz4-toast-compression
if you change a column's compression algorithm and run VACUUM FULL or
CLUSTER, the data will be recompressed with the new compression algorithm.
This is does not work for 14.2 and 14.3 (the only two versions I tested).

TEST CASE:

I run the small test from Dilip Kumar's post (2nd link above) and after the
VACUUM FULL I get this, which is not the desired outcome (both should be
pglz):
test=> SELECT pg_column_compression(f1) FROM cmdata;
pg_column_compression
-----------------------
lz4
pglz
(2 rows)