I think both is indeed important. But I also think (and wish to focus on) that if Microsoft/GitHub leadership wish to indicate that they care about systemic racism and racial bias/inequality in their workplaces, they cannot stop at language adjustments on their platform. They must put up capital.
(Also, I think that criticism that only language changes are relatively useless is not without some substance. If we had more BIPOC in our workplaces and leadership, and it is something black people in tech advocate for, then it is a problem that would solve itself because tech companies would have to choose between losing their CTO/CIO/Chief Architect/Director of Technology Platform Worth $$$$$ and adjusting their language to be welcoming to their employees.)