Interesting - would be interested in a comparison between GraphBLAS (which I had not heard of until just now) and, for example, graph-tool's (https://graph-tool.skewed.de/) underlying algorithms (Boost Graph Library).
It seems that they serve very different purposes. Graphblas is mostly focused on the processing of real-valued functions defined on the vertices and edges of large-scale sparse graphs, and is optimized for this use case (think graphs with thousands of millions of vertices). The boost graph library is not tailored to numeric functions and it will probably be less efficient for this use case.