I happen to have a stock 13.3 and 11.12 on Ubuntu here so I thought I'd contribute numbers in case it's helpful:
v13.3:
Time: 4368.413 ms (00:04.368)
Time: 837.046 ms
v11.12:
Time: 5178.595 ms (00:05.179)
Time: 1027.857 ms (00:01.028)
So I'm also seeing a slight improvement in 13, not a degradation. auto_explain and pg_stat_statements are installed in both; otherwise they're pretty vanilla.
