I really don't get your point.

Foreshadowing does not require every single fan of the series to know why x thing of note happened in the manga.

Like, I don't recall anyone thinking that scene was noteworthy outside of being impactful to the arc. If you could cite some posts from like five years ago I'll just admit I'm wrong and you're right, but I've been reading One Piece for well over a decade and have never seen anyone think that scene was particularly important outside of the arc itself.

Also, the whole point u/Momentmoment24 was getting at is that there is nothing about the panel that actually suggests things. Everything, and I mean literally everything, you're mentioning is almost a textbook callback.

A callback is described as either a relevant reference to an event that takes place earlier in the narrative, or a way to tie the loose ends of a later... A callback, when used well, reminds the audience of a previous reference

This is exactly what the scene does.

So you are basically saying that Oda lied like shit about create entire Skypiea arc with a whole different species, gods, different cultures, religious beliefs, sun god, dawn, etc. Making Wyper look at Luffy's dancing silhouette like he had seen something completely unnatural. Give Skypieans a special rythm of folk song.

Instead, you have new information and because it happens in the new scene it invokes feelings of the previous scene. Foreshadowing would be something like the Blackbeard they line. Regardless of it indicating his crew or he is some kind of multi-person abomination, it's clearly meant to be important and indicate something in the future like u/itsnotmybussiness is getting at.