I am surprised about this as well: here (EU) people I know have no issues with this at all. Friends are both male and female, for my wife and me, and we meet, alone, with them often. Colleagues as well; I often have lunch/dinner/car rides alone with my colleagues of the opposite sex and never thought about this. They are colleagues and we are there to do a job. I have never, only for highschool teachers, heard anything different than this in NL: my parents did and do the same for instance.
Probably in the group you hang around with, but you can't generalize that. There are definitely people in the Netherlands who will actively avoid situations where they are 1:1 with mixed genders, and not only in work settings. Since I have children, I meet much more people who are 'different' from my 'normal' crowd (which are successful university educated upper middle and upper class professionals) and I havr painfully felt this more than a handful of times the last two years - to the point where I've started to somewhat dread situations where this sort of awkwardness might happen.
Additionally, and this is even worse, it is starting to reinforce some stereotypes in me, and is making me less tolerant of those who are uptight like that about it. And this is not something against muslims either; I've had muslim women excuse themselves from me and I just thought 'oh well, when in Rome, do like the Romans'. It's when people are more 'like me' and behave like this that I get annoyed and think less of them (and their background) for it. As bad as that is.
(Edit: but what I hate even more is that this is making me adjust my own behavior as well. I start to feel 'uncomfortable' (oh what a horrible word) now in those situations because I realize others might be, and I certainly don't want others to feel like they somehow 'have' to be around me. I'm turning into a product of the society that produces millions of precious little snowflakes with the mental resilience and self-awareness of 2 years olds. I hope it's just part of the transition into being part of the 'old people'. At least that would make it 'normal'.)
You are right, cannot generalize. But as it's not a common subject in NL (we usually hear about things that actually happened like the Judo thing); I would find it horrible to have to be careful with everything I do because people might feel 'uncomfortable' (like you I do not like this word; I think uncomfortable is an indigestion type of thing). But this is not at all to belittle people who are generally threatened as yes, that happens, but 'we' (in NL) (and in UK I see it as well) do not have that feeling generally and that's better than this 'let's not go for a drink because I might end up fired'. It widens the gender gap considerably as well as you cannot treat others like equals. You would have that drink with a male colleague, alone etc.
I went (as a white guy) to a mostly muslim highschool in Utrecht (Kanaleneiland in the 80s) and besides guns, knives and streets fights, this feeling wasn't there either. But real (in the much more than uncomfortable range) things ofcourse happened, it just didn't leave this kind paranoia behind. If paranoia at all.
It's very common in all western countries, there's nothing special about Europe, the Netherlands or the UK. Go talk to some male primary school teachers about their experiences - if you can find any.
