More specifically, a hybrid building would be an energy efficient, or “green” building, using environmentally sensitive materials. But this usage has not become popular to the degree that “hybrid cars” has, so I cannot be positive that this is what is meant in your case.

But if it does mean a ‘hybrid’ in the green sense, I don’t think your example is one. Steel is a common, standard building material, there is little “green” about it.

Your example sounds like it is referring to structural integrity during fire.

Steel columns reach temperature and collapse more quickly than concrete — but are less bulky than concrete. So using it higher leaves minimizes bulk and weight up high, and leaves the heavy structural lifting to the more fire resistant concrete on the lower floors.