[enhray]

An example to prove your point: Flipboard determined that our current rendering engine was too slow for their needs and implemented their own rendering engine on top of ours while retaining the rest of the browser infrastructure.

[0] https://engineering.flipboard.com/2015/02/mobile-web

[_bxg1]

Yep. And as mentioned in the write-up, it brings lots of complications when it comes to accessibility. The same goes for SEO. It sounds like it was the right solution for them, but it isn't for everybody.