[davidmurdoch]

For an origin page utilizing 100% of it's available processor resources, yes.

But in the real world most websites don't do this. What likely matters to the user is that the page they're navigating to opens faster; the user likely doesn't care about the performance of the hidden tab they just came from.

Of course, `noopener` has security and privacy benefits which may outweigh the performance costs (if there are any).