As far as Zachtronics games go, you've been able to save multiple solutions since IIRC Infinifactory, and those games all have two or three optimisation goals.

I think Silicon Zeroes only remembers one solution per puzzle, however in most of its levels its goals are quite closely related.

OCTOPTICOM also only saves one solution per level, but only has one optimisation goal, I believe.

I don't believe your assertion is true; at the least, it is not true in my experience.