TSMC is not trailing. They’re so far ahead that Intel’s 18A is equal to their N5 family in density.

Therefore, N2 is 2 generations ahead of 18A by definition.

Therefore power advantage you’re referring to is backside power delivery. This is a need long term but it doesn’t bring as much power benefits as you think. TSMC’s customers don’t appear to demand this feature as highly since it’s been getting pushed back to 16A. The design change for designers don’t seem worth it yet.

By measure of density, but by performance to watt 18a is likely superior to n3. So I don’t think it is fair to say they are cleanly 2 generations ahead, more like 1 or 1.5 ahead now. Yes, n2 / n3 are overall more mature and well rounded processes at this point in time. But this is a big step for Intel and if they can prove 18a they could start bleeding. Bit of market share from TSMC.