[justaguyonline]

A Just-So story cannot be a hypothesis since a good hypothesis must be testable for actual science to be done later.

In contrast, a Just-So story will never be followed up on and simply exists to supply an easy to digest explaination for a phenomena. An explanatory meme so to speak. Hence their comparison to fairy tales via titles like "How the Tiger got it's Stripes"

[Bartweiss]

Exactly. When I see just-so story used as a criticism, it's almost always because something isn't falsifiable, and more specifically, it's usually an argument from ignorance. The explanation slots into a space we don't know much about and defends itself with "it's possible and it makes sense", but its strengths are almost always narrative rather than factual. Like Kipling's actual Just-So Stories, they're interesting and memorable, but very dissimilar to the histories we actually know.

(As far as why this specific example qualifies, it's basically impossible to falsify the story, yet it's badly out of sync with what we do know. "Wolves circling the campfire" show up in books and movies, not in real life; even absent modern tools, wolf attacks on humans are rare and reliably come from desperation attacks on isolated people, exactly the wrong circumstances for this story. Keeping predators at bay by offering food that won't sate them is the exact opposite of how things generally work; it's the equivalent of tossing out chum to stop sharks from attacking. And we have a pretty good model of how canine domestication in general began - it does involve bone and meat scraps, but scavenged from waste, and with wolves scaring away other predators, not spontaneous cooperation.)