Insider Majin Bu tweeted that Apple is working on a «stripped down» version of macOS exclusively for the iPad Pro M2, expected in 2023. According to him, it is codenamed «Mendocino» and will be released as «macOS 14» in 2023.

One of the biggest complaints about the iPad is the lack of support for desktop-class software. There are constant calls for Apple to bring not only Final Cut Pro to the iPad, but also the full version of macOS.
For greater touch control convenience, the macOS interface has been enlarged by 25%. However, apps that run on this product will still be versions optimized for iPad and not for macOS. Therefore, it is not entirely clear why Apple would transfer the iPad to the macOS interface with such half-measures, since macOS on the iPad is needed more for the sake of software than for the sake of interface.
Leaks about software testing should always be taken with a grain of salt. For example, rumors about macOS on the iPad have been around for more than a decade, and rumors about the original iPad said that macOS was possible even before the release of this device. Also, Apple likely has versions of macOS running on the iPad for internal testing and tweaking.
Another possible explanation is that it’s not macOS at all. Apple may be working to bring iPadOS functionality closer to macOS by adding a menu bar and other Mac-like interactions. iPadOS 16 already introduces a Mac windowing feature called Stage Manager, this could be the next iteration.