On my revisiting “Realism and the Aim of Science: from the Postscript to the Logic of Scientific Discovery” (1983), written around 1951-56, it is apparent that the concept of critical preference is emphasized. In considering falsifiability and falsification in isolation one might miss this.
Popper says (p65), of course we expect the sun to rise tomorrow because it is the best theory available. “Best available theory” means in comparison with other theories.
The action of comparing theories with other theories is critical. Popper (p71) replaces the problem “How do you know? What is the reason or justification, for your assertion?” by the problem: “Why do you prefer this conjecture to competing conjectures? What is the reason for your preference?”
Corroboration reports on the survival after testing. Popper was never simplistic and proposed that one might consider:
internal consistency in comparing conclusions,
investigations of the logical forms of theories,
comparing theories with other theories to determine whether or not the theory under consideration is a scientific advance,
and empirical applications of the conclusions.
Even a simplistic assertion, that the sun will rise tomorrow, can be contrasted with an alternative, the sun will not rise tomorrow. The rising of the sun as observed by humans for thousands of years corroborates the hypothesis that the sun will always rise, in non-polar latitudes, but we do not propose that the sun will always rise just because it rose before.
The expectation that the sun will not rise is not as acceptable because
1. non-rising has failed observational testing, and
2. there are arguments that are less strong in supporting non-rising rather than rising, for now.