Beta versions are always slow and sluggish. Just install the latest beta of iPadOS 18. It will be sluggish. The reason is that in beta versions there is a lot of logging and reporting running in the background which can not be disabled.
We will see. It feels worse than earlier betas; I have always put the public betas on my iPad, and this is the first time we're this late in the cycle and my iPad feels too slow. But nothing would make me happier than if this all just goes away when iOS 26 is released properly and all animations run at a smooth 120 FPS again.
1) that is not a paradox
2) the ending of the sentence (which you left out) gives context: iOS 18 beta is sluggish as well, so ‘being sluggish’ is not a liquid glass exclusive