Misleading article, OLED compared to standard IPS is more efficient at lower brightness, however becomes less efficient as the brightness and screen size increases, where there is a distinct tipping point when it becomes exponentially worse than IPS. But this is not the case on current laptops in which the brightness and size of the best Samsung OLED panel maxes out at only 500nit and 15 inches.
The real issue with the 13.3" Spectre is the pixel-dense 4K UHD resolution running on a relatively small 60Wh battery, not the use of OLED technology.
I got 7 hours of use out of my previous Spectre 13.5" with 2.5K QHD OLED paired with a bigger 67Wh battery, which would probably translate to roughly 8.5 hours in your WiFi 1.3 Browsing test, pretty decent by your review standards.
An accurate comparison of IPS and OLED should be performed with 1080p IPS and 1080p OLED models of the Spectre 13.3 using the same CPU/RAM/Storage SKU, under equal settings. And it CAN be done, since the HP Spectre x360 13.3" is the first laptop to offer IPS and OLED touch panels in an identical 1080p resolution.