Comment by dragonwriter

> Why should the browser contain a specific template engine, like XSLT,

XSLT is a templating language (like HTML is a content language), not a template engine like Blink or WebKit is a browser engine.

> Also it can be reimplemented using JS or WASM.

Changing the implementation wouldn't involve taking the language out of the web platform. There wouldn't need to be any standardization talk about changing the implementation used in one or more browsers.