...moving those numbers to something that didn't happen, would not just linearly affect the result - it would of course also make this month look a lot better.
That side-effect is a good reason
not to worry about trying to 'monthatize' the block reporting.
For example, let's just say we hashed 365% at the end of April with no block, but 15% into May we found a block. Falsely, somebody would interpret the beginning of May as really good luck, but nay, nay. It took us 380% to get that block, which isn't horrible, but it's not lucky.