It's definitely something that at least vendors knew was important. However, ARM/AArch64 chips already decimated x86 in performance per watt even when x86 chips generally had a process advantage. But ARM laptops generally sucked. Yes, the battery life was excellent: even a crummy Samsung Series 5 Chromebook delivered pretty impressive battery life for its light weight and price. But the performance? Yeah it was shit. Good enough for a few tabs of Chrome and nothing more, honestly not so bad. But the calculus for phones definitely worked out in ARM's favor.
But that's the thing. Sufficient performance per watt is very important. Improvements to performance per watt are rarely unwelcome. However... you can mislead people regarding generational improvements when touting performance per watt metrics. If the design didn't actually improve much, a new process node and pumping more power in can cover a bit. Pretty much every vendor does this at some point, and even if Apple isn't currently doing this, pivoting towards touting the efficiency improvements rather than the raw performance is not a good sign, especially considering that these chips go in desktops too, and Apple still has some ground to cover if it wants to compete fully with high end desktop CPUs from the PC market.
But that's the thing. Sufficient performance per watt is very important. Improvements to performance per watt are rarely unwelcome. However... you can mislead people regarding generational improvements when touting performance per watt metrics. If the design didn't actually improve much, a new process node and pumping more power in can cover a bit. Pretty much every vendor does this at some point, and even if Apple isn't currently doing this, pivoting towards touting the efficiency improvements rather than the raw performance is not a good sign, especially considering that these chips go in desktops too, and Apple still has some ground to cover if it wants to compete fully with high end desktop CPUs from the PC market.