Majority of these 300 instances actually are Mastodon and other microblogging instances.
They likely have imported a Mastodon-tailored blocklist at some point.
/kbin is fully compatible with Lemmy - you can subscribe to Lemmy communities, post there, up- and downwote Lemmy threads and comment under them. User of any Lemmy instance can do the same with /kbin magazines.
/kbin magazines work the same way as Lemmy communities. Almost. Owner of a magazine can assign hashtags to it, which will effect in aggregating posts from outside Lemmy and /kbin in this magazine.
Because /kbin allows you to read threads not only from "Feddit"/"Threadiverse", but also from Mastodon and other federated microblogging, in the same threaded format, categorised by magazines. (section "Microblog")
kbin.social is in particular situation, as it is the only top 15 server by monthly users, which is not Mastodon. The only Fediverse instances bigger than kbin.social, are:
mastodon.social
pawoo.net (Japanese, Sujitech)
(a lolicon server)
(two fake and one sus Russian instances).
Every other Fediverse server has less monthly users.
It tempts to try federation with Meta, mainly to try Threads' handling of the real threading app.
Meta is going to embrace ActivityPub with Threads by Instagram. Are we (free Fediverse users, creators, programmers, etc.) able to extend, and extinguish Meta's app?
Different Fedi software support articles, threading, formatting, fancy formatting (Misskey-Flavoured Markdown), video, events. I doubt, that new Facebook's app would support all of these at once.
kbin.social is only PWA right now. There is Interstellar app for Android being developed right now, but it is available only via Github releases (no Google Play nor F-Droid). And it works only on https://kbin.earth (or instances of /kbin fork called /mbin) right now.
All logos here are made artificially monochrome (ebay, Google still remain coloured, etc.). Revolut has broken its R into 2 pieces in 2023. AirBnB and Microsoft logos include now their symbols, not only wordmarks (and they are omitted in this image). Spotify still uses its "beams".
Yes, some brands went (more) bland - especially Pinterest, Google and ebay.
For fashion: Burberry has returned to its knight in 2023. And some fashion brands go against this trend - 2017 Zara wordmark is more complicated than before.
BTW, even on this image I can see, that former Revolut and AirBnB logos look like knock-overs of each other. Both used even shades of blue xd
Nobody on a Lemmy instance is able to follow accounts (like on Mastodon or /kbin). Thus, Lemmy will not fetch anything from Mastodon unless written specifically to a threadiverse community (and the community being CCed). Because of this, Lemmy instance are less harmful, than (potentially) any microblogging server (be it Mastodon, Pleroma, Soapbox, *key, etc.)