SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
They appear to relate to perf queries, and combining them with truely unknown commands would probably hide useful information. Furthermore, 0x20 is issued by every title, so without this every title would be recorded as using an unknown command, which is very unhelpful.
