Indeed. Norwegian is doing this because the optics now force them to do so, not self-assessment of the risk. They, and the Norwegian Civil Aviation Authority, failed in that regard.
The MCAS system and the way it was introduced sound a little like a patch, and slightly haphazard.
While training & runbooks and procedures are important, take-off is a busy time, and the Max-8 is (afaik) intended to operate very-nearly-like a standard 737, so it's not inconceivable that pilots wouldn't have time or intuitively know how to handle this situation.
Ultimately any vehicle/software/tool is going to be safest when the responsible designer makes it intuitive and reduces the possibility of failure cases rather than adding workarounds or runbooks to patch over them and/or disclaim the liability.
Anyway, it seems like it could be early to strongly assign blame or critique until we know how serious the issue is.
Generally do agree with grounding the Max 8 fleet as a precaution, and also given the poor engineering smell around the MCAS.
But not keen to assign blame/failure and damage reputations until there are credible investigation results, or without providing references.
It seems more likely that the plane suffers from some elemental design problems that were insufficiently patched over to pass inspection in order to protect the already invested capital.
They are just blaming the victims, trying to let those already killed pilots to take responibility for their faulty designs.
Considering that pretty much any criticism can be dismissed with "better safe than sorry, also everyone else was doing it, we had to consider the optics" it makes perfect sense to step in line and ground them like everyone else. Not doing so would just be stupid when there's near zero downside to the people making the call.
It's like highway traffic. Sure you can obey the letter of the law but when everyone else is doing something drastically different your exposure to risk is minimized if you just do what they do whether it's right or wrong.
https://www.euronews.com/2019/03/12/caa-suspends-boeing-737-...
http://publicapps.caa.co.uk/docs/33/SD2019001.pdf
Norwegian Air and Norwegian authorities had the same information (or indeed lack thereof), but did not act until now. Given the known similarities, and the lack of data that rules out a problem with the B737 MAX, the responsible thing is to err on the side of caution.
People are pattern-matchers, and if 99% of flying the plane is the same except the part that will kill you if you don't do it the new way--well, people will do it the old way and die. That's infinitely more true in an emergency situation where you tend to fall back strictly on training and instinct.
If you want to jar people into different behavior, the interface needs to be different as well. Otherwise it looks like the same old contract.
I think many of us kind of know this from GUI/API/whatever design, but there's no reason jet planes would be any different.