Yes, TG gives out a return upgrade, but there are also other considerations such as poor burn rates using TG FFP and requiring 50k per year vs. 35k on AC for example. The earn rates on each Star FFP varies so much especially in discounted Y that you really need hawk's eyes to find out exactly which program works to your best advantage.

At the end of the day, any extra benefits for being the operating carrier's own FFP Gold is mostly "nice to have" benefits that usually don't make a huge amount of difference. I think there are a ton of things more relevant such as earn/burn rates, qualification criteria etc, rather than one-off upgrades.