2. LEDs are not more efficient than double ended sodium light lamps. max efficiency seems to be around 50%. So the other half goes to heat waste which has to be managed. climate control and especially temperature control is an issue in indoor farming.
But also: Frontal heat radiation from HPS is working against condensation on plant tissue, helping to achieve good phytosanitary conditions.
Everything has its pros and cons.
2. Very few food plants are dioecious, and the ones that are (like asparagus and dates) are either ones where the fruit don't matter or are not likely to be grown indoors
In some species pollination occurs generally just with wind or movement (rather than insects), for example corn where the pollen falls down from flowers above onto the silks which are the female portion (sort of a vaginal canal if you will, i.e for every corn seed there is an attached silk). Or tomatoes which have closed flower and generally always self pollinate as the flower is blown or shaken with a very small amount of cross pollination on occasion. Pretty cools setup with these type of plants, massive reproductive efficiency through mostly self pollination but a little bit of crossing occurs as the occasional foreign grain of pollen gets from another plant so there is genetic variation.
2. LED lights are pretty efficient, and they provide another avenue for optimization (e.g. color, intensity, timing, etc.). Whether or not those optimizations are financially effective is probably situationally dependent.
3. LED lights provide latitude independence. No idea if this is a serious reason, but I could see it being of interest to Iceland.