JmanEspresso wrote:If I weigh out the amount of 2 double shots, add them to the hopper, and EITHER, grind it all, dose PF, pull shot, dose again, pull again.. I get very different pulls.

Yes, because for many grinders, the grind setting drifts coarser as the weight of coffee above the burrs changes (aka, "popcorning"). If you grind per shot, the grind will be coarser towards the end, but at least it will be consistently inconsistent, if you know what I mean.

There's 1g+ of stale coffee that gets ejected the instant the grinder starts. If you grind 1, then 2 you have the stale coffee, the extra weight of the 2nd dose in the first shot and fresh[er] coffee and more of the 'popcorn' effect on the 2nd.