Semantics is part of the problem here...
The term "surface tension" has been used around here for quite a while. It is not quite an accurate term for discussion of water on hones. A more accurate term is "wettability."
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Some hones, because of their more glass-like surface, cause water to bead up on the hone rather than spreading as a uniform film over the honing surface. When honing with such beaded water, you are basically honing on a dry surface and the blade tends to push the beaded water right off of the hone.
The point of adding something to the water to increase wettability, or decrease surface tension, is to keep the water on the hone so that the serves as a lubricant between the hone and the blade. It has nothing to do with viscosity.