Nah, the 24% number is pretty much meaningless, especially with 4pc T20.
With 4pc T20 you'll always have 24% haste during the ED window as long as you have 21% haste from gear since you can't cast a starsurge without picking up a stack. In fact, the 24% number is just a number you need to fit an extra GCD in between starsurges plus using both empowerments. Most of the time you don't even want to do that with the ED rotation anyway. You only want to do it if (a) you've got an OI proc to use (b) you need to refresh dots or (c) you need to squeeze in an unempowered solar wrath if you. Those situations are all relatively rare and can always just wait a bit to be used with higher haste from 4pc T20.
I tried a bunch of Sims with SimC and with AMR and got the same results. Anywhere from high teens to mid to upper 20s for haste is pretty much the same dps. If you have too much haste you'll start to lose mastery. There's so much variable haste from gear and procs that it just doesn't matter what your haste from gear is as long as you're in a pretty big window.
Even with the old ED it turned out (confirmed by e.g. slippykins over at mmo-c) that the 30% haste break point wasn't even important once we started hitting nighthold. It was really only important in EN and ToV level gear it seems.
I think the machine learning windows are pretty damned solid for moonkin. Try to get above 8k haste and mastery (and really, as much as possible). Try for between 2k and 6k crit. Try to keep vers lower than 4k. Anything in those windows is good stuff and fits with the general consensus from mmo-c/discord/gebuz etc. advice for gearing.