Mitigating impact of long running read-only queries

https://www.postgresql.org/docs/current/sql-set-transaction.html

"The DEFERRABLE transaction property has no effect unless the transaction
is also SERIALIZABLE and READ ONLY. When all three of these properties are
selected for a transaction, the transaction may block when first acquiring
its snapshot, after which it is able to run without the normal overhead of
a SERIALIZABLE transaction and without any risk of contributing to or being
canceled by a serialization failure. This mode is well suited for
long-running reports or backups."

If I use these three properties together as below, would WAL buildup be
prevented, or will the system still be causing a backup of the WAL for
logical replication during the entire duration of my long reporting query?

BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY DEFERRABLE;
--long report query
commit;