I think this is too complex of a situation to nail it to a single factor.
The average temperature drop has been shown to be a reliable way to force hybrids to bloom, which is why it is so useful and has led to the explosion of their sales.
However, that will work well with some species, but not others. A long time ago I observed that phalaenopsis species with primarily white/pink/purple flowers seemed to need that, while those with red/orange/yellow blossoms did not.
If you look at the geographic origins of the species, generally, that second group tends to be more equatorial than the first, so that makes sense, as the seasonal changes are practically nonexistent.
Light is certainly a factor, but I doubt it’s as straightforward as the temperature stuff.
Some of the best flowering phalaenopsis I’ve ever seen were grown in a hot, humid greenhouse that was so algae covered that it was dark. When I was a new grower and had not bought into “more light is better”, I had phalaenopsis that stayed in bloom for 6-, to 9 months at a time - they were grown in a windowless kitchen with the only light being a sliding glass door about 20 feet away.
Just this spring and summer, I observed something that would make me believe more light is better - after they have experienced a significant cool down period, my plants spend winters in my kitchen, up against north-facing, Low-E windows. Spikes were forming and growing slowly, until I moved them outside for the season, where they are located just outside those same windows, so get the same, indirect light, but more of it due to no glass-coating reduction and because they then had a bright, open sky above to add scattered light. They exploded into bloom and many continue carrying them now.
So how can “growing them dark” and “giving them more light” both be good?
[Putting on the biggest “speculation” hat I can find]
The only thing I can guess is that it relates to resource accumulation and the bit of adaptive ability the plants can muster.
Plants grown on the darker side always are darker green, courtesy of added chlorophyll, suggesting their metabolisms apparently adjust (within reason) to a lower-energy input lifestyle. With reduced input, I suspect they must accumulate a larger “storehouse” of phytochemical resources before blooming, but when they do…POW!…it is very well “fueled”.
Contrast that to a plant grown brighter. It has greater input and often moderates that by being paler, it with the input being steadier and faster, it can afford to bloom more often, albeit with less “fuel”, so can be smaller and relatively short-lived.
It also may be that those “privileged” plants, experiencing a steadier input, are less in need of a “seasonal trigger” to bloom, as they can afford to expend the resources more easily than can the darker-grown counterparts.
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Hybrid Mode
