Why isn't my game running in worker mode when using remote preview?

I've set the Use worker project config to Yes and can confirm that the game runs in a web worker. However, when I use remote preview and run the game on my iPhone 11 (Safari, iOS 15.4.1), the game does not run in web worker any more.

Any ideas why this is happening?

Could be disabled or just not supported in that browser. Try updating the browser or seeing if it works in chrome.

It is supported on Safari 15.4.1 (reference: https://caniuse.com/webworkers). I've also tested it on Chrome and it's not running in a Web Worker.

The other weird thing is that the game is running at 30 fps on Chrome and 60 fps on Safari (on the same phone, both not in a web worker).

The fps difference was due to Battery saving mode! But the web worker is still off in both browsers.