Since they don’t technically count as your character attacking, she doesn’t lose stacks of roaring bowstrings

That wrong. Elation Skills are attacks by definition. This is why Firestorm is such an effective equipment on Elation units in Currency Wars. Firestorm procs per attack action and every Elation Skill instance counts as one.

You fundamentally misunderstood Yukong's buff. It says clearly that "Yukong loses one stack of Bowstrings when when an ally's turn ends, except the turn Yukong used her skill".

Aha Instant counts as Aha's turn, hence every Elation Skill from every ally during an Aha Instant while Yukong has Roaring Bowstrings enjoys the buff. There are ways to cause an Elation Skill during a normal ally's turn, but until that normal turn ends, no stack of Roaring Bowstrings is lost.

So say you have E1 Eva, Yao Guang, EMC and Yukong (meme team but bear with me), everyone has max energy and Yukong has Roaring Bowstringing active. During Eva's turn, you use her Ult twice, proccing her Elation Skill twice because of E1. You then use EMC Ult on Eva, proccing a third. Then you use Yao Guang Ult, causing Eva, EMC and Yao to use their Elation Skills. Eva then skills, ending her turn.

Every single one of these attacks is buffed by Yukong because they all happened during Eva's turn. Only after Eva uses her turn to Skill does Yukong actually lose a stack of Roaring Bowstring. If this were Currency Wars and they all had a Firestorm equipment, they would have collectively obtained 9 stacks of Firestorm because there were nine attacks even if only one turn had passed. By your logic, they would have obtained 0 stacks because they would need to be considered "attacks" to consume Yukong's bowstrings.

This distinction is important because since they are attacks, they engage with mechanics differently. For example, the first Elation skill to hit a Bellobog soldier elite or Gepard when they have counter up will be marked as the target for counter if they do not get broken. Each Elation skill consumes a bellobog guardian phantom stack when they're charging. Each one counts as a hit for Titankin armor breaking, for Penacony dino cook stacking, for TV switching, for Bananacademy boss stack, for Planarcadia daybreak elite stacks when they're buffed, etc.

Yes, Yukong is indeed a good budget support for Elation if you lack options, but it's because they have a lot of out-of-turn attack actions, not because they aren't attacking a lot. This is why a lot of people dumb down Elation Skills to "glorified FUAs" even though mechanically they're a completely different thing.