My friend Ray said," “Overwatering can kill orchids”. Nope. Insufficient air to the roots does it. "
Darn right, Ray. I think understanding principles is much more important than having "rules," which presumably are based on the principles but may not be understood. And what I'm learning from semi-hydroponics confirms what Ray said, but I take it further. I'd say the principle is that every plant (often based on genus or species, but of course these are "mixed up" by hybridization) has an ideal air/water ratio (which includes the environment it is in, particularly humidity, which is of course a ratio of air and water). These vary quite a bit, particularly by genus. So on one extreme, one has say, Tolumnia, and on the other perhaps Phragmipedium.
So, when I see that a plant is "too wet," it might be just as accurate (perhaps more so) to say "it doesn't have enough air to balance that amount of water for those particular roots." In addition to temperature, humidity, light, etc., one must also consider both medium and container. So, for example, I have a society friend who also grows S/H who can use a denser (wetter) medium in her house than I can in my greenhouse (40% to 90% humidity difference or thereabouts). When I receive a plant from Norman's Orchids, it will be in moss in plastic. I will immediately put it into clay because the clay breathes and the plastic does not. And I can water it twice a week with my S/H, which I could not do in plastic. I have a photo somewhere of a Catt growing in a fairly fine S/H medium but in clay, and the roots are great. In plastic, they would be rotted.
And beyond that, in S/H I have to consider the layering of the leca (medium). It tends to get very dry on top, so some genera (including both Paphs and Phrags) seem to benefit from moss on top of the medium.
Yes, too much water in the ratio can kill roots, particularly if they are not ones newly grown and adapted for that amount of water, but one can say it's too little air for that amount of water. Actually, I'm amazed at how wet some vandas in moss can be if they are in a basket, and same for Phals in clay. One can also get more air to the bottom of pots either by using "orchid pots," leaving the bottom empty as Gold Country does, or even using an inverted plastic net pot down there.
On a related note, I'm also having some success using living (local) moss, which is abundant here in the NW, in a net pot rather than imported sphagnum.