"This jutsu is lightning"
Surely this explanation from the creator of the jutsu himself should carry some weight.
we dont accept calling something light to be enough evidence for something to be light speed and that is why concrete and more explicit things like speed of light are required to get something accepted as light speed, for the same reasons we don't need to assume just because it is a lightning it will only be lightning speed or that it's hard capped at lightning, it does not even conflict with the actual speed statements either
lightning in fiction (if supernatural in nature) is allowed to be ftl, mftl, immeasurable speed based on their feats / statements either from the source material or from feats against other characters
though manga and explanation of the jutsu shows otherwise.
not a single thing in the manga remotely conflicts with anything the manga says
I can say "most men of x company generally earn 500K per month so be aware of mr. Y as you're trying to flex against him" and then the story can later reveal said man to earn 1 trillion per month, there's no contradictions, it's simply laying the world-building foundations for what lowballed value is to be applied to the general characters/things of a specific category in the absence of greater, more explicit information
It reads to me like it's entirely plausible these statements themselves either don't understand the difference between lightning and light fully or is being liberal with the terminology for the sake of effect.
brother, Kishimoto of all people knows what he's talking about, he is a powerscaler author, he's written
this series with this
typa wank and
this and
this and
this and
this
he's also taken his main inspiration from
this, he doesnt often dive into super explicit stuff within the story of naruto unlike S8 because it breaks the narrative flow that he's established for his world, the databooks don't have this issue so he's able to freely dump light speed statements several times to his desire, the idea that he's not aware of the scaling arguments that he repeatedly puts out is just blatantly untrue
Well, a lot of people refer to the light itself as the lightning
this never happens in the naruto series (outside obvious similes) kishimoto never confuses the two terms and he's attributed light speed towards light beams as well (he's also added photon guns being used into one of his novels so we know he's fully aware of them and what they entail)