SIMD = Single Instruction Multiple Data, meaning the same instruction being applied to multiple different values simultaneously. That's exactly what GPUs do.
That's exactly what GPUs do in a single thread, but GPUs are also about threading, usually sporting tens, if not hundreds of small cores to effectively allow them to compute that many pixels (or rather shader outputs) in parallel. Otherwise, it wouldn't scale much.
That being said, I understand you only wanted to point out the error in the upper post.
SIMD = Single Instruction Multiple Data, meaning the same instruction being applied to multiple different values simultaneously. That's exactly what GPUs do.