Here is the specific Google Flight I selected: https://www.google.com/travel/flights/s/yYPhNC6aXX4VP5cj8

Here are the screenshots: https://imgur.com/a/X923fSo

That's an issue, and going from kayak to delta for same flight leads to same issue.

I wonder if this is some bug/edge case for really close in flights? The example flight booking takes off 2 hours from now?

Last time I ever tried to book a flight so close the online sales funnel was closed due to post-9/11 security restrictions. I think 2 hours is about as close as is even legal right?

Can you replicate for a flight tomorrow / next week / next month?

In my experience this replicates routinely for Delta Main Cabin fares for non-elites on leisure/non-corporate travel once only “Preferred Seats” are left in the economy cabin.

What I think the other carriers do well is detect when there aren’t non-charged seats available for advance selection, and remind you that you can continue without paying for a specific seat and still be guaranteed a seat on day of departure.

Delta hand out “free preferred seating” as a perk to all sorts of categories of traveler though. I wonder if that complicates the prospect of offering that kind of warning.

Urgency is one of the key motivators for using dark patterns. Wouldn't be surprised if Delta defaults to "1 seat available at this price" for all busy flights within X take off time regardless of the availability.

I see, thanks.

On an entirely different note, this feels like an exclusively Delta fuck up (and they know, given that they built a whole pop up for it). I fly United and American extremely frequently and never seen this. I have even booked Alaska basic economy that doesn't give you a seat and been given a free seat selection. Delta has been rapidly going downhill in recent years -- those that nerd out on air travel know exactly what I'm talking about.

I expect these patters from all low-cost airlines, so fly Alaska whenever possible.

I used to fly between Portland and SF often and Alaska was the only airline that never screwed me.