The continual expansion of web standards for one off devices and use cases only ensures that only Google can afford to build a browser.

It's a proposal. And if it gets built will be in Chromium.

The usual lifecycle for these things now is propose, implement, gather data from usage experiments, refine, and standardize.

There will also be statements for or against from the other browser vendors and interested parties.

This is meant to work with other android devices too. It explicitly says so in the introduction.

Microsoft has actually contributed quite a lot to web standards over the years.

Plenty of OEMs have made and are making multi screen devices. Some of them have even been market successes (Nintendo DS?).

What's wrong with blink?

Standardization-wise, it was just fine.