Hmm, I'm hardly an unbiased observer but that thrillist article doesn't ring very true to me. Yes we're forthright and don't tolerate things being dressed up well and appreciate honesty over platitudes but it's not as extreme as made out to be. What I do think happens is that it amplifies in translation because (I think I've mentioned this previously) our grasp of English isn't really that great the language is just familiar. Since everyone tells us it is so good we're never encouraged to improve it, so it's a combination of forthright in a limited word capacity that's utilising words that resemble Dutch ones that don't necessarily have the same meaning in English = blunt or rude depending on delivery.
Customer service was pretty bad here for some time on par with what I experienced in London the last time I was there (just uninterested or dismissive) but it's improved here at least in the last 10-15 yrs mostly due to foreign investment in retail but most people are horrified by it and really look aghast if there's someone greeting you at the door like in most American shops.
We also don't wish death by cancer on everyone, we just add (although it's hardly done and no longer considered ok) it to swearwords to amplify them eg. cancer cunt (except we pretty much use male genital bits for swearing exclusively). Typhoid is still considered ok to amplify as it's no longer a common deadly disease, so that gets used mostly, albeit rarely, it really is reserved for extreme anger. Swearing generally not done very much, I never swear in Dutch but have no issue doing it in English 
There is a contingent of (mostly white youngish men, socially conservative and economically liberal) who are very cultish about saying it like it is, but you have those everywhere now with the rise of populist politics. Boris Johnson calling veiled women postboxes is an example of that. We think they're just dickheads too and it's nothing to do with the Dutch identity but it does seem to get conflated by those people which feeds into nationalism.
I do feel we're encouraged from a young age to disassociate criticism from ourselves, so if someone is saying you look fat in something it means they're blaming the item of clothing, they're not insinuating you're fat, they're mad on your behalf at the item of clothing. It is a sort of care, at work it's an acknowledgement that the person making the criticism is trying to examine their part in something not going right, it's a form of forensics and assessing where they went wrong. We're also taught from a young age that what someone says about you is usually nothing to do with you but a reflection of themselves, it is an odd form of exposure/sharing and we're generally not voluntarily forthcoming on that front.
I do think it is mostly about not encouraging untruths though, we're not that old of a society and we don't have a resonance of mythicism and esotericism stemming from an ancient culture like other European nations and treat it with a heavy dose of scepticism. Religion has been dogmatic whenever it's had any hold but merchants have mostly ruled the roost and left their marks subsequently.