"How do you claim on one hand that YC can materially improve your company, and on the other judge the company for not being improved after going through another accelerator"
Not all accelerators are equal. Going to college may or may not change your life. Going to Harvard, Stanford or MIT probably will
But if you've got a degree from a lesser colleges, then Harvard, Stanford or MIT will judge you for (i) choosing to go to that less prestigious institution[1] (ii) not obviously being a class above your peers in that cohort (iii) wanting to improve yourself with another bachelors degree in a different discipline rather than something more academically or professionally stretching...
[1]even if you had really good financial or location-based reasons for it...
Not all accelerators are equal. Going to college may or may not change your life. Going to Harvard, Stanford or MIT probably will