Each job has affinity for another job's abilities, from 0 to 100. Affinity of 0 means you cannot use those abilities. Affinity of >0 to 100 means that the higher affinity, the more closely your recast timers, cast length, and power approximates that of the original job. Conjurer has 100 affinity for conjury skills. I think Thaumaturge has like 70 or 80. Archer has considerably less.

Therefore, the one with nature ability does not help conjurer, but on every other battle job it decreases conjury timers, speeds up cast of conjury spells, and increases power of conjury spells by effectively 10% relative to a full conjurer.