Are we really using 23 bytes on most machines?

Hi,

https://www.postgresql.org/docs/current/storage-page-layout.html
"(occupying 23 bytes on most machines)"

Is this still true? At least on Linux it is 24 bytes:

postgres=# select pg_column_size( row() );

 pg_column_size  
----------------

             24

(1 row)

Regards
Daniel