“Go” or “hardness” (as it is commonly translated into English) is misleading. “Go” in Japanese has a much fuller meaning than simply “hard”, as this to me seems to imply rigid or inflexible. If we look at other examples of the character “go”, we can get a much better idea of what it means.
剛健 Goken – sturdiness
剛直 Gochoku – integrity
剛勇 Goyu – bravery
Looking at these other words using the character “go” we can see that it implies not only “hardness” but stability and strength. In this sense, this is what San Chin kata is trying to accomplish IMHO. To build a strong foundation both mentally and physically for the student. Perhaps a better term for San Chin would be Kiso-gata; literally “foundation kata”.
The term “Ju” has similar problems when translated as “softness” and used as a descriptor for Tensho / Rokkishu. A favorite misnomer of mine is Judo “the gentle way”. At any rate, if we look at a few more examples such as:
柔順 Jujun – obedience
柔和 Juwa – tenderness
We can see that the connotation is more along the lines of flexibility, not gentleness. Again, in this sense it is not a bad descriptor for Tensho / Rokkishu, in that this kata is trying to impart the concept of flexibility and yielding IMHO.
Are “go” and “ju” the best terms, not with the current English definitions, but with a little more explanation, they can be beneficial. At least in the case of beginners.