That was already possible with Travis CI though. Not sure how the situation is now, are they still up and running?
The difference is habbit.
We are not in the habbit of doing this now.
This change may change that habbit and encourage a new one.
Im not saying it will, but its naive to brush literally every suggestion off because you can already do something similar.
At least think it through before making a judgement on a new idea.
Personally speaking, I'd be worried that I end up making 15 commits to get everything right and the history in that PR would be slightly embarrassing. Having the live linting, intellisense and tests makes pushing a single commit a lot easier.