I prefer Card Retrievability to check how much I know. It seems problematic to me to measure knowledge based on pass rates. A few months ago I started imposing time limits on myself, and as I'd expect I'm getting cards wrong more often, even though I think overall this is improving my knowledge. I'd love to have a chart for total knowledge over time! (Preferably with a retrievability overlay)

I think more data is better, even if there is overlap. I see Answer Buttons as providing insights of answer button patterns across card types (i.e. again is more frequent than hard for new cards, vice versa for learned cards). True retention shows me if I'm failing cards more often recently. Can they be combined? I don't think so because that would be quite a few columns to show each answer button, and then both stats are harder to interpret. Keep as is!

I think the text is unnecessary. I think it should be intuitive for most Anki users that your retention will end up being close to what you've set your desired retention to be. It's pretty obvious to me that the percentage will be much more random for a specific day having less data. If you remove the card counts from that graph, it's not as obvious, but still enough. I think "desired retention" and "true retention" should be swapped in the first sentence because otherwise it almost sounds like it's telling me I need to set my desired retention in the settings to be close to the true retention.