I've also heard that it's dependent on difficulty, but the percentage thing is floating around too. I honestly have no clue, I think I might've gotten the same video for both my normal and hard playthroughs but I have no idea.
And the last time you see Scarecrow, Croc drags him into the water. Croc himself falls into the caverns under the island and it's not really a stretch that he escapes.
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Gamertag-Murphiroth
Pokemon Black-1978-9490-1161