There's no formal cross upgrade program across Skyteam members. For example, you can't get upgraded at all on KL/AF flights as they don't allow comp upgrades for their own members. Upgrades at AM do not work like they do at DL. There's no automatic addition to a list as far as I can tell and there may not be an actual list at all. Their top two tiers can request at up to 72 hours, but their lowest Gold level can only do it at the airport. There's no formal documented policy for upgrades for Skyteam Elites and I would expect them to be treated no better than their own lowest level (DL also does not have a formal policy for other Skyteam Elites). It's possible they can't add/confirm you at check-in and it can only be done at the gate. Here's their policy for their Gold level --

• You can request it when checking in at the airport where your trip starts
• For the Member and a companion traveling on the same itinerary and PNR.
• Subject to availability in Cabina Premier
• Paying public fares Y, B, M, U, K, H, L, Q, T, E, N, V, R, and W.
• Includes flights to or from the U.S. and Canada, Central and South America.
• Not applicable to or from Buenos Aires, Santiago, Sao Paulo, Europe and Asia

https://www.clubpremier.com/us/gold-level/