Eduan did say V had the best tension among companions BUT he didn't say orbs are the best tool for people with great tension. He said high tension is needed to make an orb. I doubt tension even is a skill which pertains to a specific shinsoo combat style (as in, fisherman or wave controller). Rather its a general skill which applies to everything.
If tension was a skill which pertained specifically to wave controllers or shinsoo control then logically V would have been the best wave controller among the companions. Also, look at the role tension played during the hidden floor. The gang learned their shinsoo's qualities. Learning them makes shinsoo easier to control and make larger bangs as eduan demonstrated. Which in turn provided a significant power boost to every single regular who mastered this. Aguero, androsi, rak... All got a significant tension boost. And their skills are not necessarily that of a wave controller.
Which fug symbol are you talking about?
Thats the only fug symbol I recall.... Unless that is supposed to be a black orb of sorts? That'd be weird.
That said, the idea that V symbolism and... easter eggs if you will are all around fug makes sense. But there are a few things to consider. The flare wave is a signature of fug but it is taught by jinsung. And jinsung goes all "I AM A SPECIAL HA" when using his ultimate move on kallavan. So which is it? Is this a special ha move or a V move? Both? Does that make sense? Jinsung is incredibly old and has enormous influence within fug as even slayers and elders are wary of him so it would make sense that he was actually the one that introduced the technique. I proposed earlier that the technique was perhaps meant to primarily deal with those who have particularly tough bodies. Which fits pretty well with jinsung as well.
That said, if V was the one who came up with the technique originally it would make sense for fug to adopt it. As everyone within fug would (only in theory) have a technique meant to kill zahard. But as far as killing zahard goes, that goes regardless of who brought that technique to fug.
As a side note, while the technique does not require strength or a tough body I do think those are important for someone who uses the technique. The as explained in the series causes you to lower your guard. It leaves you basically defenseless. If it works you basically succeeded and exploding your enemy from the inside (though data zahard and kallavan somehow survived this). If it doesn't work and you are up against a physically powerful enemy you are probably taking a few hits. So having a tough body that can take punishment is a huge advantage. A tough body significantly compensates for the technique's main risks.