As far as I know this has been an issue with DL.com for half a decade if not more.

There's no such thing as "bait and switch" in terms of buying airfare. No State consumer protection laws apply to the sales of air travel.

However, there is federal "Unfair and Deceptive" trade practices. Which is deemed at the sole discretion of the Secretary of the Department of Transportation (DOT). The DOT typically only becomes involved when there are a lot of complaints about something. I suspect the fines DL might get hit with are chump change compared to the amount of revenue the "technology limitation" generates.