This translation is not the correct one.
On the red it says: '' In the past he was a rival of Mihawk, which can conclude that his sword skills are among the best in the world ''
The word 'swordsman' is not said.
They were rivals in the past, they were supposed to dispute the WSS title when the Shanks still had their original arm.
But the word '' your sword skills are among the best in the world '' doesn't mean shit.
Kizaru has sword skills among the best in the world and he does not dispute the WSS title
Big mom has sword skills among the best in the world and she does not dispute the WSS title
Aokiji has sword skills among the best in the world and he does not dispute the WSS title
The fact that Shanks has sword skills does not make him compete for the WSS title. After Shanks lost his arm, he no longer disputes the title because Mihawk believes that without his arm he is not the same swordsman as before (this is indeed true). Mihawk is no longer interested in Shanks and Shanks is no longer interested in Mihawk. The Shanks became yonkou even though their sword skills were below the Mihawk, which clearly indicates that the Shanks acquired secondary power, parallel to the sword skills.
On the red it says: '' In the past he was a rival of Mihawk, which can conclude that his sword skills are among the best in the world ''
The word 'swordsman' is not said.
They were rivals in the past, they were supposed to dispute the WSS title when the Shanks still had their original arm.
But the word '' your sword skills are among the best in the world '' doesn't mean shit.
Kizaru has sword skills among the best in the world and he does not dispute the WSS title
Big mom has sword skills among the best in the world and she does not dispute the WSS title
Aokiji has sword skills among the best in the world and he does not dispute the WSS title
The fact that Shanks has sword skills does not make him compete for the WSS title. After Shanks lost his arm, he no longer disputes the title because Mihawk believes that without his arm he is not the same swordsman as before (this is indeed true). Mihawk is no longer interested in Shanks and Shanks is no longer interested in Mihawk. The Shanks became yonkou even though their sword skills were below the Mihawk, which clearly indicates that the Shanks acquired secondary power, parallel to the sword skills.
They are still rivals. That is why everytime we have the character relationship chart, it is said that they are rivals.
The fact that he competes or not for the WSS title is totally irrelevant. Shanks (or anyone else for that matter)never compete to be the WSM or the WSC, does that mean that he was stronger than WB or is stronger than Kaido?
The Yonko title is not a strength base title which why Luffy can be considered to be an emperor. So the fact that he became an emperor after losing his arm is not a proof that he gained a new power. In fact, we canonicaly have a hint on how Shanks became an emperor after losing his arm, and it is because his commanders are stronger than the average one which is why they were highlighted in the marines meeting.