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.
The special case doesn't appear to make a significant difference in any games, and the current implementation has a (minor, fixable) issue that breaks Super Mario Sunshine (both with a failed assertion (https://bugs.dolphin-emu.org/issues/11742) and a rendering issue (https://bugs.dolphin-emu.org/issues/7476)). Hardware testing wasn't able to reproduce the special case, either, so it may just not exist.
PR #9315 contains a fixed implementation of the special case on all video backends, and can serve as a basis for it being reintroduced if it is found to exist under more specific circumstances. For now, I don't see a reason to keep it present.
Pokechu22