In Australia we typically water gardens at night because we lose less water to evaporation. At night with lower temperatures and consequently higher relative humidity and far less wind, these conditions mean much less evaporation and more water to the plants. In hothouses with a captive atmosphere this would not apply. I imagine this would also increase the likelyhood of fungal problems as you state, something that has not been a problem to me.
Very interestig. Thanks for your patient explanation.