To rephrase the question: If Snatch boosted an item's drop rate to 11% from 10%, would that be a 1% bonus across the board, or a 10% multiplicative bonus to each item's drop rate? Or some variable rate applied to each rarity tier? Does it affect the rate of appearance of platinum chests in event battles? What about the contents? We don't have the data, or even the intuition, to begin to answer these questions, though a fixed-rate multiplicative bonus seems most likely.