Web technologies are default-slow while native (except Java on Android) is typically default-fast. One needs to go out of their way to create a slow native app, even if it's of course possible.

Slowness is the natural state of web applications and creating a fast web application is much more difficult and requires a senior team with knowledge about browser implementation in order to avoid or work around the performance pitfalls.

I also have the feeling that such performance comparisons are done with the assumption that the apps under test are almost the only thing running on the machine. If every applications were to start 10 processes taking 1 GB of RAM things would get uncomfortably slow.