I don’t think your test is objective.

A browser made with native Java/Kotlin which then has to setup an environment for running HTML, Javascript and CSS, is obviously going to be slower and heavier on the battery, than an app made in just Java/Kotlin

You don’t realise it because you have a fast enough phone probably. My 5 year old cheap ass phone can’t run Voyager or other PWAs without major stutters, but Jerboa works perfectly fine