Interesting. This is basically what I was getting at, but definitely species specific. Based on what I know about the species I'm keeping it would likely be detrimental to fluctuate temperature so I have no intentions on doing so. I would venture to guess that the vast majority of species sold for the hobby do not require any fluctuations which is why there is not much published about it.
Your question was a good one because, as you can see, there are species that require seasonal variation to maintain health.
In contrast, the majority of fish that we keep in our aquariums live within a range of temperatures, but their health doesn't depend on this variation.
For instance, discus withstand temperatures between 78-93 degrees ( depending on areas endemic too) in the wild within a given year. However, both ends of the extreme lower and upper temperature numbers are experienced seasonally by discus in a time-line of days or weeks. The majority of the time they are within 82-86 degrees. The point is that discus dont depend on this variation
in temperature to survive.
Although, temperature variation does have a part to play in reproduction. Temperature variation, along with the influx of fresh waters from rains and flooding into rivers and tributaries, hormone changes in fish, and certain seasonal food species and availability of this food source, all induce spawning and breeding behaviors.