Lemmy web data usage

Watching the network tab of Chrome when I have a Lemmy instance open I can watch the websocket data coming in from the server. Even though I have "Subscribed" communities selected, the data stream seems to contain all post data (at first glance it looks like new posts and vote changes) from all communities federated to the instance.

It's manageable for the moment but if the network grows a lot, that could end up being a huge amount of data that's sent to users and probably not desirable if users are on slow metered connections. Is this by design?