5Is this "caught" grammatically wrong? No
Does it always have to be "had caught" to express a preceding action? No
Is it so strict or does it just sound awkward? your sentence is acceptable.
I know in "I called him before I went to school", "called" doesn't have to be "had called" due to "before".
ex) He caught a fish from a river. The next day he went down to the river where he caught the fish. If that first sentence is there, the second is acceptable.. If the first sentence is not there we definitely need 'had caught'.
Student or Learner