I saw the post in the Facebook group you are referring to, and that was Jean Roboker who posted to you about your birds. Jean is the Grande Dame of Dutch, and if it's her feeling they are not true Dutch, then I would certainly bow to her judgement. Jean has been breeding Dutch for decades, and as you can see is very passionate about them.
Likely what you have are "Dutch Bantams" from a hatchery, and in Jean's mind, those are not true Dutch at all (and I am inclined to agree with her, fwiw.) Hatcheries have crossed Old English Game Bantam blood into some middling quality Dutch they bought from breeders years ago, and now what they are selling at first glance may look like a Dutch, but when examined closely it's easy to tell they are not (which is why I asked for better pictures, taken from the side, because side views are the easiest to tell pure from crossed.)
Please don't be upset with Jean, she has worked for many, many years to advance the cause of purebred Dutch, and as a lady in her late '80s, she can get somewhat cranky about it, which I hope you will forgive her for.