amok: For quite some time. At the beginning there where complaints that the main page did not show the banner, so Steam added it. Seems like they missed on channel, though.
P1na: I just don't see those banners myself. Anywhere. I honestly don't know why, but the banners could have been there for years and I wouldn't have seen them. I see the DLC purple banner, but not the early access blue one.
I guess this invalidates a big chunk of my complaint: it's not that the warning isn't there, it's that I don't see it and so it has never existed for me. This begs the question of why I don't see it, some kind of browser incompatibility? But no matter if it's Firefox, Chrome, or steam's own client, the blue banner just isn't there on my PC. On either one of my 2 laptops, I should say. And it shouldn't be a country thing either, because I travel around a lot and so I've seen the store from many different countries. It seriously puzzles me.
Do you have to activate some option to see it, maybe?
That's strange.... I do use the enhanced steam addon. Maybe it is that? Let me check.
edit - no, the only option there is to hide EA games completely.
I guess the banner image is blocked on your computer, as this is added after the store page load (there is a slight lag), while the DLC banner is part of the picture. I think it is this way, as a DLC will always be a DLC, but a EA game may go out of EA at some point, and it is therefore no need to get new icons?