That source is the often reliable Ice Universe on Twitter. Across two tweets, we've learned the alleged updated display aspect ratios for the Galaxy Z Fold 4, and the battery capacities for the Z Fold 4 and Z Flip 4, the latter of which the leaker is apparently "100%" on.
ExclusiveInternal screen ratio:Fold4：6：5，Fold3：5：4External screen ratio:Fold4：23：9，Fold3：24.5：9May 9, 2022
Let's address the Galaxy Z Fold 4 display rumor first. For the inner display, the ratio is apparently moving from 5:4 on the Galaxy Z Fold 3 to 6:5 on the Z Fold 4. It sounds like a subtle change, but that will make the screen quite a bit squarer than the current inner display.
The outer display of the Galaxy Z Fold 3 uses a narrow 24.5:9 ratio. This will become a little better on the Galaxy Z Fold 4 according to Ice Universe, who says it'll have a 23:9 ratio instead. That isn't as big a difference as we'd like, but it would at least be an improvement on the phone's usability when folded up — right now, it's comically and awkwardly narrow in phone mode.
If we look back at an older leak comparing the Galaxy Z Fold 4 and the rumored Google Pixel Fold, the Google foldable could use a similarly shaped internal display but a smaller, wider outer display. That leaves the possibility that the Pixel Fold will be easier to use in phone mode, but that's all speculation right now.
100% Fold4 4400mAhFlip4 3700mAhMay 9, 2022
As for the battery capacities rumor, 4,400 mAh in the Galaxy Z Fold 4 would be no different from the Galaxy Z Fold 3. This isn't surprising given the above tip suggests there won't be much of a size difference between the current and upcoming Z Folds, but we nonetheless hoped that Samsung would do more to give its flagship foldable a battery life boost, since it was one of our main complaints with the Z Fold 3.
The battery drain issue is even worse on the Galaxy Z Flip series than on the Galaxy Z Fold series, so hopefully the rumored combination of more capacity and a more efficient chip (possibly the Snapdragon 8 Gen 1 or Snapdragon 8 Gen 1 Plus) will help the Galaxy Z Flip 4's performance on our custom battery test. However, the rumored larger outer display may drain a bit more power and offset the capacity increase.
If Samsung keeps to its previous precedent, we should see the two new Galaxy Z phones arrive in August. That's not too far off, but make sure to check back with our Samsung Galaxy Z Fold 4 and Samsung Galaxy Z Flip 4 hubs regularly for the latest rumors before then.