No, because they think that 3 admirals is the bare minimum to be able to do it. An admiral can kill an admiral as well, that’s an admiral level feat. Beating 2 yonkos amongst 3 individuals put each as admiral-caliber — beating the 2 yonkos is more impressive.
Beating 2 yonko was 3 individuals is canonically seen as something admirals are expected to be capable of.
Killing the admiral is way more impressive.