Diggity said:
it's just a marketing move.
The whole idea is that you find these places on Uber Eats/Grubhub and think it's some new spot you hadn't heard about. If their marketing data shows that the typical "food delivery customer" might not have an affinity for Denny's (for example) but loves to try new places. Wala!
They don't expect many people to do full recon on these spots.
Has nothing to do with marketing.
In these specific cases, they initially struggled as brick and mortar under covid. Saw the potential of delivery revenue while minimizing their second biggest cost (labor they can't get anyway). Most are focusing on a new menu different from their B&M even if their appears to be overlap. If it was marketing they'd have to change concepts quarterly or so.
True Ghost kitchens are built specifically for this and have nothing to do with a name brand. Some are even just food trucks. They run 5-10 concepts that are delivery only and make good margins. Often better than sit down restaurants.
And no, food isn't much different than of eaten on site. Advances in packaging, warming, and distance allowed for delivery ensure that.