Question about pg_dump + pg_restore + pg_toast

Hi,

Checking one of the databases, we have the schema below with size as below.
I just rename it as abc, this is the one we want to dump and restore.

schema_name | schema_size
--------------------+-------------
public | 656 kB
pg_catalog | 6608 kB
pg_toast | 412 GB
information_schema | 104 kB
abc | 187 GB

We are upgrading this database from v12 to v16 and we want to do a dump of
it in case we decided to do a restore from v16 to v12.
SO, after the upgrade, in case we want to rollback to v12, we will do a
pg_dump using v16 and then using v12 pg_restore
When we do the dump, does it take into consideration the size of pg_toast
as well? So it will be 412+187-GB :( ?

BTW, was pg_toast created automatically by PostgreSQL? Reading on
https://www.postgresql.org/docs/current/storage-toast.html, there is no
mention of it.

Any feedback is much appreciated. Thanks in advance.