When I booked a ticket using two fares (P & D) which were labelled "Restricted First", I did not realize that this is what they meant to call it:

Further, please allow me to offer a short explanation regarding our
fares. The special coach fare you had purchased include a complimentary
upgrade, if seating is available, in the forward cabin. However, they
are a coach fare, albeit higher than some of the discounted leisure
fares, and unfortunately a fare adjustment is not due. Again, I
apologize for any misinformation you received regarding this airfare.

Ironically, on the same day I got this explanation, I also got an email from DL saying (quote):

Thanks for flying Business Class and come back soon.

Methinks I see both sides of their mouths moving simultaneously. Feel free to weigh in.