That seems to be the case. The listed games are Aspyr's most successful (non-64-bit) games on the MAS. C&C Generals, RCT3 and The Sims 2 are even almost constantly among the top 10 of the charts of paid games on the MAS.
It's nice of them to update old games, but to drop support of the 2014 Borderlands game is not.
And it's not as if Aspyr systematically updated their games to Metal in the process, like Feral does.
The games listed above also happen not to be among those that Aspyr removed from sale in June.
So it is my understanding that all other 32-bit games won't be updated.
I'm not sure why they would update a 2003 game (SimCity 4) and not a 2014 game (Borderlands tPS). I guess these decisions are based on sales.
Actually 5500M 4 GB is about 240% faster than 560X in Unigine Heaven Ultra 1600x900 according to this review.
5300M 4 GB is ca 270% faster than 555X and ca 24% faster than Vega 20 in Unigine Heaven Extreme 1600x900 according to this review.
I think iMacs will get this GPU update next year so we don't have to wait two years again for the next update. They probably will get the desktop versions.
1600*900 is not adequate to test GPU performance, neither is Unigine 1. It's much too old.