I'm not surprised. This was expected behaviour. Those who said otherwise were just in denial.
HOWEVER:
1) The intended target of the iPad Pro is more for content creators. Blooming as shown in the images is most noticeable in rooms with very low ambient light. This is not an ideal lighting for content creators. Ideally, content creators would have proper room lightning and in this context the iPad Pro would usually be superior with much higher peak brightness, and sometimes more accurate colour production.
2) The intended target for the non-Pro iPads is more for content consumers. Blooming for those customers can be a real annoyance, since a lot of them like watching videos in the dark. In that context, lower peak brightness is not as much of an issue, and usually the colour balance is good enough as long as it's close.
Put me firmly in the category 2. I am not much of a content creator. Occasionally I do create content on my iPad, but it's not often, and it's not to make money. I make birthday videos and such, but watch Netflix on it much more. OTOH, if you're a YouTuber editing in LumaFusion a few hours a day, then you're much better off buying the iPad Pro.
I'm looking forward to an OLED iPad Air in 2022, sold alongside a mini-LED iPad Pro 11" in 2022.
As for the iPhone, people don't generally do critical work-related content creation on an iPhone, nor do they do it for long, long periods of time on an iPhone.