Not suggesting in any way that the withdrawals have not all been for completely legitimate reasons, but, I do remember hearing once that Cup of China is historically the least favorite GP for skaters to be assigned to, due to distance, scheduling, logistics, etc.
Have no idea if that’s true or not, but if that’s so, it’s possible that it’s a factor in whether a skater might choose to withdraw from an assignment here rather than push themself to compete when not 100%