Everyone who cares to know about generational improvements have indeed compared performance between tiers. No they have never been conctant but the "best" generations clearly had better segmented tiers in their generation compared to prior. Adding "fake" frames to say the 5070 has the performance of the 4090 like Jensen, tells you even Nvidia do this comparison.
You're missing the point. The only thing that makes a 5080 a 5080 is that's what NVIDIA named it. of course comparisons are going to be made but it's meaningless to expect the numbers to correlate to some specific performance gain over the lower tier or previous generation.
The lineup is different every year. The metric that matters is performance per dollar, not the name of the product.
The 80 tier isn't great value this generation. That doesn't make it really a 5070.