It depends what metric you're using. If you use HTM (half turn metric), slice moves count as 2 moves because you're moving effectively 2 outer layers. If you use STM (slice turn metric), a slice counts as 1 move. I would say brody's video is referencing a well known thing that crosses take at most 8 HTM to solve; I don't know what the count is for STM if it is different.