"Achromat" means without color, and, as I've read one quip, APOchromat means without color "but we really mean it this time". So does Semi-APO mean between Achro and APO (implied) or semi-color free which might put it short of an achromat?
I think semi-apo exists but is a moving target that is mostly marketing hype. The real measurements of a lens's color correction is buried in the specs deep enough that only experts can decipher it. The name is irrelevant since the meaning is neither clearly defined nor rigidly enforced.
Each manufacturer has their own standard definition, some may change over time though, but agreement across the industry is lacking. Too bad resellers don't even the field when they sell competing products by certifying or grading the instruments performance.
I know, buyer beware
... and I try, like most of you. But it seems that experience and a deep pocket is the only way to really understand what is right for an individual.