i really haven't read much about growing in coco but i've noticed yield is great and they have a lot of discussion about dry downs, dry backs and how that influences growth as well as using that to manipulate plants. so for them i don't think that keeping moisture consistently the same throughout the grow works to their advantage like it does for organic soil growers.
roots uptake water because of osmotic pressure which is influenced by how much water is held in the medium and the amount of salts gets higher the dryer the medium gets. this video explains everything and really ties it all back to plants in the end of the video.
so after i learned about that, i became curious if that is why the hand watered design seems to work better over the auto top off where the water level is always the same. at first, my hypothesis was it had something to do with the water table below creating some sort of pressure or force which pushes water inside the plant which is sorta true and called root pressure but this pressure can only drive water upwards a few feet, so it is not the main way water enters plants which is called water tension cohesion theory. most of the plants grow great in the irrigated design and it is soooo helpful when you have a stuffed room full of SIPs to be able to add water to all of them outside the room via the reservoir. i can also just add so many gallons to the reservoir and then each sip will get an equal part of the water, so i can still control the moisture if i wanted but still have the option to fill up the reservoir to go on vacation. its really just this fussy mac1 plant that grows ok in the irrigated SIP but when she is in the handwatered design, she prays more. it is also cold here 9 months of the year and with the water table below, inside the pots, it can be more difficult in winter than warmer seasons to get plants to pray and such. the other plants don't seem to care but i really like this plant so that is why i started redesigning the SIP system recently. i think i can do things to the design which will influence how high the water will travel up in the soil so there will be more air in the root zone. it will be a while before i can test my theory with the rotation of the plants right now.