Perform scan on Toast table

Hi everyone ,I have a question. I have a table with large data (i was used
bytea datatype and insert a binary content to table ) so that Postgres help
me get a TOAST table to storage out-of-line values .
Assume that my table is " tbl_test " and toast table oid is 16816

When i peform EXPLAIN ANALYZE select query on tbl_test ( EXPLAIN ANALYZE
SELECT * FROM tbl_test).It show that sequential scan was performed on
tbl_test ,but when i check pg_toast table with this query :

SELECT
relid,
schemaname,
relname,
seq_scan,
seq_tup_read,
idx_scan,
FROM pg_stat_all_tables
WHERE relid IN ( SELECT oid
FROM pg_class
WHERE relkind = 't' ) AND relid = 16816

I saw that seq_tup_read = 0 and the seq_scan is always is 1 .idx_scan is
increase arcording to the number of query on tbl_test

I was wordering : Do have a sequential scan perform on tbl_test and other
index scan will be peforming on TOAST after this sequential scan ?
Can you explain this dump question to me ,please ?
P/S : sorry for my bad English .Thanks ! :)

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