I think you are likely correct, but the assumption you are making is that there is no "next level" of physics that we aren't even close to breaching yet. Like how we went from classical mechanics to quantum physics. It changed basically everything. If there is some other deeper thing that explains some of the many things we can't explain with our current models, it could lead to crazy new physics that would be very hard for us to understand. There is no guarantee that it would be as understandable as what we have now. It could be 1000x more complex or something.

And then imagine that there might be a level beyond even that one that is 1000x more complex. We just don't know. If all we have is the physics that we know about right now, then yeah everything will be explainable to us but also the "power" of the AI will be severely limited compared to what people traditionally imagine when thinking about the singularity. There will be physical limits to what even the super-powered AI can do.

Bottom line, I think we just have no idea of knowing what is going to happen. That is why it is called the singularity.