It is meaningless because it cannot be defined or measured, it is not quantifiable.
You need to be discussing air filled porosity which is measurable.
The discussion is not about clogging of the drainage holes, it is about how much water is retained by capillarity after draining.
When you say 1/16" grains I guess you are saying the fraction retained after sieving with a 1/16" mesh. If so then the smallest grain size is 1.75 mm going upwards. I use a 2mm mesh size and this works for me in my climate, which is hot and dry, I'm guessing much like your climate. I would think, for a material with very fine pores like turface, (that is, no inherent porosity in which air may be retained after draining, such as with pumice) is too small for a cooler, wetter climate. In cooler, wetter climates there will be lower evaporation and transpiration from plants so the water held by capillarity will persist for far longer then a climate like yours. A larger particle size will have a greater air filled porosity and a lower saturated zone after draining, making for a healthier plant.
Grain sizes of 1mm will not clog a drainage hole, but the saturated zone held by capillarity will be very high and roots may well suffer from lack of oxygen. Combine warm, wet weather with low oxygen levels in the soil and conditions are perfect for phytophthora and other soil pathogens to infect the plants roots. Fungal attack is the main cause of root death in plants, not anoxia, in fact phytophora will not attack a plant root in anoxic conditions, it only attacks in low oxygen conditions within a specific temperature range. This is why air filled porosity is the important measurable factor of potting mix structure
Paul