Note that Sunday doesn't care (at all) where mismatches occur. The "natural" way to add Sunday: follow pure C-P unless/until it finds a mismatching position. Pure C-P then computes a specific shift. Nothing about that changes. But something is added: also compute the shift Sunday suggests, and pick the larger of that and what C-P computed.

C-P and Sunday both have cases where they can justify "supernaturally large" shifts (i.e., as long as len(needle), or even that +1 for Sunday), and they're not always the same cases.