That's true when the difficulty is going up, and it's the exact opposite when the difficulty goes down, I know this should be very easy to understand but I had a very hard time explaining that to someone some time ago, I don't know if it was lack of comprehensive skills from their side, or I just suck at explaining things (probably the latter is true).


It's as simple as understanding that the work done on epochs with lower network difficulty has a higher effective value, doing 30T work when the diff is 30T is not the same as doing 30T work when the diff is 60T, your luck in the first epoch is a lot worse, using 60T for the entire calculation will make your stats look better.

Anyway, I don't think pools like Ckpool do that on purpose, it's probably just the effort of having to store more data, also given that pool luck is just history it's somehow irrelevant unless the stats are bad enough to make you think that pool software/hardware is bad and is losing blocks, aside from that -- it seems like nobody cares.