Magazines are different from Communities. Magazines include both the forum element (called a Group in ActivityPub parlance, and is what Lemmy calls Communities) and the microblogging element. Magazines can have Mastodon(/Misskey/Pleroma/Friendica) hashtags associates with them and collect posts from those platforms into the magazine's "Microblog" tab.
Lemmy doesn't do that. Communities there are only the forum element.
Also, there being groups on different websites that use the same name really isn't a call for them to be aggregated. They're different communities, with different people using them.
Consider @politics instead of @python. Can you imagine how @politics might be a radically different community than @politics? Is there confusion there? Should those communities be smushed together?
Turning back to @python, r/Python is a pretty big subreddit. Possibly too big for most peoples posts or comments to ever get noticed by others. That's not a community. That's not a space where most people can have meaningful discussions. Having a dozen, or a hundred local Python communities where people actually get to know each other, get to have their contributions or questions actually read, and get to feel like they're actually part of something, rather than just shouting into the noise, is a feature, not a bug.