Why are communities on Lemmy.ml more full compared to the same on a different Lemmy instance?

https://lemmy.sdf.org/post/13415

Why are communities on Lemmy.ml more full compared to the same on a different Lemmy instance? - SDF Chatter

For example, I’m on Lemmy.sdf.org [http://Lemmy.sdf.org] and I joined the [email protected] [[email protected]] community. But there are many missing articles and comments. If I browse directly on Lemmy.ml [http://Lemmy.ml] for the same article there ~90% of comments are missing. https://lemmy.ml/post/1152794 [https://lemmy.ml/post/1152794] has 26 comments https://lemmy.sdf.org/post/11232 [https://lemmy.sdf.org/post/11232] has 0 comments

This could mean that syncing is in progress between these two instances. In that case, if you check back in a bit, you should see all the comments.
Would you mind elaborating on this a bit or linking to documentation that explains this in more detail? It seems that unless I visit any thread on its own instance, I'm not getting the actual number of upvotes and/or comments. Waiting and checking back doesn't seem to solve it (double checked on a post I checked about 4 hours ago, still can't see the full thing), so maybe it helps if I know what's going on exactly.
Yeah on Lemmy.sf.org the [email protected] community has most comments missing. But stuff like [email protected] seem to be synced better. Maybe there wasn't subscribers for Apple community until I subscribed? So now it is just slowly starting to sync up? If so how long does it take and how many days back will it got to fetch comments?

To add another example here, I saw the same behavior on this post: https://lemmy.ml/post/1136642. Right now it has 43 comments on lemmy.ml but over on my instance (link) there's only 18.

It's also unclear to me why some posts are not showing up, since the new ones (4h ago) appear, some old ones (7d ago) too, but some ones in the middle (6d, 5d ago) do not, which doesn't really make sense...

What is your favorite NFL team? - lmmy

Let’s get this community going! I am a fan of the New York Football Giants, and I’m hoping for another fun season now that Danny got some weapons.

Yeah this is pretty frustrating especially being it seems this asklemmy community is working fine…? Hard to grasp what’s going on with comments. 😕