there were two lead developers from FFMPEG on Lex Fridman's youtube channel who talked about performance gain from assembly. They claimed the opposite

https://www.youtube.com/watch?v=IUo0UwZOaRw

Yeah, a corner case (streaming) and good developers working very hard.

The original SSE (SIMD) extensions were actually written with this use case in mind. When they first came out, the compilers were awful. They've since caught up.