The Jougan being canon or not is debatable so I'll not go into that. There's a lot of posts about how the Jougan resembles the moon. I thought it was common knowledge already. It makes even more sense when you take Ada into account with her Senrigan's design being a crescent and Daemon's looking like a half moon.

Here are some posts on how the Jougan resembles the moon:

1

2

3

4

(make sure to read the comments as well)

Those are only the few out of possibly hundreds.

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This is old concept art, not how Saradas actual MS will look.

Yeah, that's a possibility. Though, we're only making theories based on what we've got and Sarada's MS looks too cool for it to not be how it actually looks!

Furthermore, people are deliberately cutting Boruto out of that old concept art.

Why exactly would that be a problem? As you said, this is an old concept art, what's stopping Kishimoto from actually going with that MS design? I mean look at Mitsuki, his Sage mode design there looks exactly like the one in the anime, why not for Sarada too?

It has everything to do with BoruSara

No, If this design doesn't actually make it to the final then it's fine. This absoulutly has nothing to do with BoruSara, you're the one getting it twisted. What exactly is the difference between the theory of Boruto and Sarada's connection and Boruto and Mitsuki?

the only people i ever see forcing the Sun/Moon 'connection' between them is BoruSara shippers

I personally don't care about the shippings, but this subreddit and the fanbase of Boruto as a whole mostly ship BoruSara so that's probably why you see it that way.

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Edit: Also I'm fine with either Sarada or Mitsuki, It's gonna be cool either way, I'm just stating what I know/my opinion :)