If you don’t know the reasoning behind not coding for VST v3 then you can’t really say that “they did not see any advantage” or that “VST3 was not good enough”.
The first statement presumes you know something about NI and its reasoning,and the second is a statement about VST3 itself, technically.
Yes, but “not worth the effort” typically means “not worth the expense”. That may be true, but it doesn’t mean that they don’t see an advantage to VST3 or going for it, just that it doesn’t make more money (perhaps that’s what you meant), and it also certainly doesn’t mean VST3 isn’t good enough.