Though why do we not see any such rapid tolerance for other conditions for which Abilify is prescribed?
Pure speculation, but it could be along the lines that because ME/CFS patients have trouble acetylating (as the link posted by @wigglethemouse details), that throws out epigenetic regulation a bit. ME/CFS patients would be shifted towards histone deacetylation rather than histone acetylation.
Benzodiazepine tolerance — involving the down-regulation of GABA receptors caused by benzodiazepine use — is driven by histone deacetylation (removal of the acetyl molecule from histone), according to the paper I linked to above.
So if Abilify tolerance was similarly driven, you might expect tolerance to build up faster in ME/CFS patients compared to other people.