All the Columbus top end tubes of the era that were CrMo ended up being termed "Cyclex" (a patented name, sometime in the mid '80s); later tubes with the same model names (e.g. "SL", "CROMOR", et al.) were made from a new CrMo alloy called "Omnicrom" (I think fairly recently c.2020), "Nivacrom" was another patented name for their next CrMo alloy from late '80s into the '90s and beyond. I do not not know if "Cyclex" steel is still used by Columbus today in bicycle tubing applications.
I have verified that the "AIR" fork steerer tube did have ridges on it. It was probably identical to the "SL", et al. steerer since there was no change in the alloy, and of course no manipulation of its shape; although the wall thicknesses and butt length may have differred from "SL" steerer. The fact that your steerer has no ridges again calls into question its actual model (complete "CROMOR" fork; hybrid fork with "CROMOR" steerer and "AIR" blades, etc.).
I would love to trust empirical data provided by maufacturers and examples given by themselves and owners; but there are, in my experience, many outliers that contradict what is documented (Colnagos and Rossin are a prime example). Many times in post catalog publication/mid-model year changes are made and variants to models are produced that are never reflected in documentation by the manufacturer and are sometimes due to relieving themselves of odd or old stock materials, and that are made in very small quantities and are not continued into the next model year's line-up. Who knows? It happens with framebuilders working in large and small companies, as well as component manufactuers. I have a bespoke frame made in 1986 from tubing (Reynolds Special Lightweight) that was discontinued nearly 8 years or more earlier so nothing surprises me at this point.
I can only hope that you (or myself) find an identical example with its original livery intact showing marque & model decals, as well as tubing decals. That will probably be the only way to clear up the mystery and allow you a means to accurately install the proper decals, and from then on be able to describe the bike with the confidence knowing that no assumptions are being made regarding its identification.
I am making notes in my Olmo entry for my Italian bikes reference database with everything you have discovered, and I will annotate the entry as an "open case" still needing further investigation.
To just clarify; you have found no serial number or other distinct marking on the frame or steerer tube (sometimes there is the frame manufacturer's mark there aside from the tubing manufacturer's stamp).
Again, I will not disagree with your assessment based on the example you have found, but I cannot, at this time, satisfy myself 100% based on the existing anomaly of the smooth steerer tube on an "AIR" fork. If I find another known "AIR" frameset using a smooth steerer tube on its fork then I will assume that at some time Columbus created a variant fork set, or builders themselves possibly used a different steerer tube to provide a different ride quality from the helical ridged reinforced steerer tube since I doubt that one detail would have been much of a cost difference.
Not sure that I can add any more to help, but if I do discover something else I will provide you with the details.