I see consistency. In the batches with 1.75 qt/lb, you see that more mash time gets you more extract. Which is what you'd expect. Another thing you can see, as expected, is that, in general, a thicker mash, allowing for more sparging, will allow you to rinse more extract out: you seem to be doing better with 1.75 than 2. So why is 1.4 not even better? Because at some point, the mash will thicken to the point where it is more difficult to fully hydrate and get the enzymes into the grist to convert it and get the extract diffused out into the wort as quickly. So there's a Goldilocks set of conditions, the right combination of mash consistency, amount of sparge, and mash time, which for you looks to be something like 1.75 and 90. Try that across different recipes and see if they come in closer to each other, keeping in mind that the grain bill will also have a noticeable impact: crystal and roast malts just don't contribute as much extract as base malts, which is why we use base malt accented with specialty malts.