What does the "ReadOnlySpan<byte> debugNameUtf8" do in CommandBuffer.BeginRenderPass(...)?

I am trying to update my SRP to Unity6 and as I do so I moved some things to CommandBuffer, namely BeginRenderPass. But unlike the ScriptableRenderContext it has an extra argument ReadOnlySpan<byte> debugNameUtf8. I set it to a string but it doesnt show up anywhere (profiler and frame debuger). It isnt even listed in the parameters section! So what does it do?

Also as a side note, what is the differance between ScriptableRenderContext.BeginRenderPass(…) and CommandBuffer.BeginRenderPass(…) routes?