On iOS, a PWA requires a splash screen image to be supplied in the source code of your app for every single iPad and iPhone size that exists (that's 25+ individual images).
iPad OS splash screens in landscape mode
However, you may have noticed that on iPads, specifically in landscape mode, your splash screens look stretched. Why?
Well, this is because of long-standing bug still not fixed by Apple (as of November 2022). Instead of using the supplied landscape splash screens, Safari uses the portrait splash screens and then expand them to fit the screen.
Unfortunately, there is no way to fix this. We'll have to wait for Apple to issue a fix. Note that this bug exists in some iPads that run iPad OS 13 or later. Older iPad typically don't have that issue.