Pure speculation: This is about visionOS. Photo editing is the least friction "pro" task to bring to a spatial computing platform.

The other options I considered:

⁃ Renewed interesting in pro use cases in general. I don't see enough incentive for this. Apple's historical interest in this was winning over creatives, but particularly creatives interested in photography are already won.

⁃ Apple wanted the tech for something on iOS. I don't think there's enough "special sauce" tech Pixelmator has to justify this. Pixelmator's tech is only valuable as a full package.