Postgresql – postgres does a row or table locked by one operation can be accessed by another op in a single transaction

I am beginning to understand how transaction and locks work in databases.

So in a very higher-level understanding:

BEGIN -- txID: 1234

UPDATE tbl_1 SET field = value WHERE id IN (1); -- for simplicity
-- Locks acquired on rows with ID 1

UPDATE tbl_1 SET field = new_value WHERE id IN (1); -- just for dumb reason updating the same row again.
-- does this operation still wait for the lock from previous operation?

COMMIT -- txID: 1234
-- Locks released on row with ID 1

It’s my understanding that all locks within a transaction are held until the transaction commits.

So in that case, how does the 2nd operation proceed on the same row that is locked by 1st op?