I got the 20 from the same wiki page that listed all of the adventures, and they were all from 2008 to 2010.
Could you name them then?
Honestly, I can only think of <20 published adventures for the entire duration of 4e, let alone just the first two years. Unless we're including
Dungeon.
And you're misunderstanding the point. I'm not talking about page count. I'm talking about level range, and have been since my OP. All of those listed are only for a very narrow range of levels, which is what I've been saying is what I'd like to see.
So you'd be happy with a 256-page adventure with five levels of adventure?
The listed adventures all feature a narrow level range because the products are small. The two go hand-in-hand.
So yeah, it's not accurate to say that 3e only had "some" of these adventures, and this has been going on for 15 years, as he said. The numbers don't lie.
But you're giving a list of adventures published over a span of eight years including small encounters published on the website (likely content cut for space) and small experimental products quickly abandoned (Fantastic Locations series).
If WotC felt they could make more money making small adventure
they would.
For my part, the desire for mega-adventures and APs baffles me. I want small bits of content I can easily put into whatever my campaign happens to be doing, without having to sort through the chaff of a big book for the wheat of the one dungeon I intend to use, and without having to sever all the connections it may have to the rest of the module it's in.
Larger mega-adventures are desirable for a couple reasons.
One, they're a full campaign. If you're busy or don't know how to write adventures, it's months of gameplay.
Two, they're a story. You can enjoy them just by reading. You "play" the adventure twice that way: once in your head as you guess what the party will do, and again at the table when they invariably do something else.
Even if you can play, you can engage in the hobby by buying the same adventures.
Third, you can pillage them for content: dungeons, locations, NPCs, monster stats, or simply ideas. It's not any harder to mentally cut away text in a module; it's arguably just as easy as adding the story necessary to connect a story-less module to a campaign. If I can add a slavers module or the
Steading of the Hill Giant Chief to my game I can add the hunting lodge from
Hoard of the Dragon Queen or the hill giant lodge from SKT.
Fourth, from a brand standpoint, larger stories are easier to coordinate events across multiple types of media: the video games, miniatures, comics, board games, novels, etc. So a fan of one is incentivized to look for other products.
This also creates a sustained shared dialogue. Everyone in the community is talking about the same thing at the same time, and can share stories of their experience with the adventure.
I understand it completely from a business perspective. For WotC/Paizo it's way more efficient to sell a lot of copies of a few things instead of a few copies of a lot of things. But here's the deal with that: as a consumer, I don't care what the vendor wants, and I'm under no obligation to do so. I want the product I want.

Whether or not they want to or will produce it, doesn't alter what my preferences are.
And I'd like a boxed set with a sturdy cardboard box, a cloth map, and several large books for a price similar to what I remember paying in high school.
WotC is a business, not a charity. If they did whatever we wanted without concern for efficiency and what would sell they'd go out of business and the D&D brand would vanish, joining the ranks of forgotten Hasbro brands like Visionaries, MASK, Inhumanites, Glo Friends, and so many more.
And the thing is, it's not just WotC, it's retailers. They talked with several store owners who complained that the small adventures are harder to sell because they're invisible when stored on shelves.
Plus the classical modules with their loose covers, maps, and such tended to be shrinkwrapped. Which made it impossible to flip through the product in the store. You have to buy sight unseen.