Currently Goodnotes on Android, Windows or even web isn't even close to feature parity with its Apple versions. I don't think it's a good idea to develop 2 separate versions of Goodnotes for different platforms.
Yes, eventually the versions might converge in terms of feature parity, but that will likely be a very long time. And even then maintenance would be problematic, as well as the development of new features, since there 2 different versions with different tech stacks and bugs, at the very least. This would likely perpetuate what is going on now, division; a main version — which has everything and is better version — and the alternate version — which doesn't have everything and is worse.
If instead the Apple version codebases were converted to a tech stack, which could facilitate easy development for all platforms at once, then Goodnotes could be easier to develop for all platforms, likely faster compared to developing two versions, which are at very different points of development. This would also mean, that the overall software could also be further improved in terms of polish, since now it wouldn't seem like a waste of resources, because the improvements would go to all of the versions at once.
Yes, converting a codebase is not an easy task, and the platforms are different, but at least having most of the code shared among the different version should be a huge improvement. I think it's a way better solution in the longterm than maintaing two different version.

goodnotes being a web app on both android and windows makes it much more laggy and the delay is much more noticable. it would improve the user experience if it was finally converted to a native app.