I mean, anything that reduces incoming heat is going to keep the interior cooler; the question is by how much? You’d still have to have a door of some kind, so it would never be perfect.
But there’s houses that are built all or partially underground, or have roofs that either reflect sunlight or otherwise reduce/eliminate its ability to heat the interior of the house. So the idea is not that far off from the same principle.
Hell, just using a roof that does something with the heat reduces interior temps a good bit. I’ve seen a house with solar water heating on the roof stay a few degrees cooler, and that’s only the roof that’s insulating anything. I suppose you could do that on every surface and get a bit better results.
But direct sun is only part of what makes an interior hotter. You can have a house surrounded by trees that gets a bare minimum of sun and it’ll still be within maybe five degrees of the outside air. Our house is mostly shaded, and we do stay a little cooler than neighbors that don’t have big ol’ trees playing bouncer for sunlight. If it weren’t for humidity, we’d use the AC a lot less. A few days ago it was 90 outside, and “only” 85 inside, after a nice rain where we had shut the AC off and opened the windows to enjoy it. It wasn’t truly comfortable, but it wasn’t so bad as to be unlivable for short spans either.