Its because it gets reported as the app using the screen and other subsystems during time its in-focus. So really it’s mostly your screen/wifi/etc using power, not the website as such - but the phone categorizes relevant power draw to the active foreground app that’s preventing the phone from sleeping.
There are only 3 possibilities
Voyager is a website in a wrapper. I dunno how it’s suppose to run the battery anymore than Safari does.
Its because it gets reported as the app using the screen and other subsystems during time its in-focus. So really it’s mostly your screen/wifi/etc using power, not the website as such - but the phone categorizes relevant power draw to the active foreground app that’s preventing the phone from sleeping.