The way to tell who is "marketing/coding" is the flight number. If it's AM123 then it's Aeromexico and follows the percentage of distance flown rules, if DL123 and follows the normal Delta earning by dollars spent.

Check out:
https://www.delta.com/content/www/en...-partners.html

Class Exclusions: If a class is not listed, no miles are earned. No miles are earned for Award Travel.

Other: Flights operated/marketed by Aeromexico Connect are also eligible to earn miles.

(1) Partner-marketed flights will earn miles based on a percentage of distance flown* as determined by the fare class paid. Unless otherwise noted, mileage credit is only applicable to SkyTeam-marketed flights operated by a SkyTeam member airline. Mileage credit is not applicable to a SkyTeam-marketed flight operated by another airline.

(2) Medallion Qualification Miles (MQMs) are used as a counter to determine SkyMiles Medallion Status. Flights and itineraries eligible for MQMs will earn a minimum of 500 MQMs per segment.

(3) Medallion Qualification Dollars (MQDs) apply to Medallion qualification. Flights marketed by the partner will earn MQDs based on a percentage of distance flown* as determined by the fare class paid.

(4) Medallion Mileage Bonus is based on Base Miles earned: Diamond - 120%; Platinum - 80%; Gold - 60%; Silver - 40%

*For purposes of calculating mileage credit and MQDs, "distance flown" means the calculated distance between origin and destination, as determined by Delta in its sole discretion, regardless of the actual distance traveled on any individual flight.