It’s more about "could give consent".
You're not wrong but that's still the part I'm not a huge fan of. I think the moment we start arguing whether something is okay based on if a fictional creature would be sapient enough to give consent or not, we're in a bit dangerous waters because that same train of thought is used by real life animal abusers: "My dog is so intelligent, I can communicate with it and it's sexually mature. Obviously it would give consent if it could speak."
That's why I personally think the better way to look at it is to draw a clear line between reality and fiction and just treat fiction as fiction where none of this matters.
Also, wanna make it clear I'm not trying to invalidate how anyone personally looks at this matter. Just pointing out the flaw in the logic if trying to "justify" furry porn with "tests" like this.
Who could deny such a good boy? *pats head*