I will say I think arguing “from the narrative” is actually valid and one of the most important ways you evaluate potential outliers
the issue is what SB specifically calls breaking the narrative, and what actually breaks/contradicts it are completely different things
when they are arguing that JoJo characters can’t be ftl because it breaks the setting/narrative/etc they aren’t arguing it against anything that the author is actually stating in the story, they’re arguing it against their personal opinion on what should be realistic or consistent for that setting, and whether they are hypothetically right about this or not it’s a fallacious argument. FTL Stands doesn’t break anything because Araki has constantly reiterated and shown us that stands can move and punch and perceive things at this level.
Bringing up “they should be able to run around the world then” not only doesn’t make much sense (fiction generally treats reaction speeds as higher than travel, jojo just has a bigger discrepancy wrt this), it isn’t actually brought up in the story as a possibility or issue at all. This kind of hardline approach also falls apart when you realize that even low level supersonic characters should not take anywhere near as long as they do to get places. As an argumental tactic it doesn’t hold up for any measure of superspeed, their subjective disbelief just isn’t being suspended here so they throw out the feat.
JoJo is an extreme example of this, but even series with a much average higher power and speed like Toriko, look how long it can take them to travel their planet. It’s everywhere in fiction, it may as well just be a trope at this point.
Honestly, this isn't even new at all to any series in fiction as you stated, the issue is when you have Spacebattles, CharacterRant and more try and ultimately force in the "narrative breaking" as an actual VS. debate for only series they think it makes sense for but never really understand how stupid it is to use at all.
Saitama can apparently move FTL... but it takes him hours to find crime to keep his Hero standing afloat? Or to get to the battle in progress? No one says shit about that.
Or how about Deku not being able to easily make it back to UA Island and needing to hitch a ride from Star and Stripe's Air Force Entourage despite the fact he should be able to outspeed those jets by leaps and bounds?
Notice how they never bring this up but they will very clearly say that Servants moving Relativistic "breaks the setting" despite having clear reasons why they can't run that fast all the time:
1. It's the equivalent of doing a marathon sprint to get to your UFC Match, you think you won't be gassed out wasting energy getting there?
2. The issue isn't short bursts at all, hell, the series explicitly show throughout all of it's fight scenes the issue is never short bursts, it's continuous use of speed is where the problem is.
3. They may be able to move at those speeds... but their extremely vulnerable Masters CANNOT! Why would you leave the person keeping you around open for counterattack in the first place? This is why most Mages only do that when they completely fortify their bases or have you explicitly locked down(and why F/SN was such a mess compared to every other known HGW, even compared to Apocrypha)
It's either pure ignorance or calculated ignorance to push agendas and it's why it's such a pain in the ass to deal with people like them. Hearing people legit say Medusa's Pegasus and Iskandar's Gordius Wheel can only move 400-500KMPH over absolute bullshit(The former is from Shirou's POV which even the game itself doesn't stand by and the latter is explicitly a lie not just through how the text goes against it but the very feat of it going from 100 meters apart to 0 in less than a blink of an eye), especially when that means the Servants move faster than their own rides by a gargantuan degree by their own abilities is absolutely retarded.