The AI will upgrade resource nodes beyond what a player can.
Each node has generator points and then a tier progression. The AI is able to upgrade the tier progressions multiple times.
This was a 3v3 game with 5 AIs. If a player upgrades the tier of the resource nodes, the AI will generally not touch it anymore. If it is the AI upgrading it, they will finish then do it again. They are upgrading all 3 tiers at the same time on the left picture.