It is not going to pass through FDA, but thats not the point.
Yes, and the reason is that it's neither robust nor reliable enough.
I mean, a medical team on Colombia is even using car parts to build ventilators. And printed 3D parts.
That's the part about it being "better than nothing". The chance of the Pi failing is probably a lot lower than other causes of death, in this case. So, if the Pi saves lives that would've been lost without it (because simply no practical alternative was available within the needed timeframe), it's a good thing. But, after the crises passes, I hope any sub-standard ventilators are replaced.
I'm not even opposed to the idea of using something
like a Pi, for this. Seriously, if Broadcomm and the Pi folks would build an industrial-grade Pi, I'd be fine with that.