>>637024chan absolutely always has been against other websites with similar interests. Where you do think the phrase "back to [x site]" and images like this one originated from? Heck, even up until recently saying you were a crossboarder on /a/ could earn you a ban or at the very least a ton of smug anime replies.
It's only been in very recent years (I'd say starting in 2014) that users from other sites have been "crossing over" to 4chan. There's that famous image that shows how the massive spikes in userbase during GamerGate and the 2016 election, and those users didn't just find this site out of the blue - they come here either to support the cause, to be against the cause, or because they think it's le epic meme zone when they see 4chan screencaps posted on any of the aforementioned sites.
Also, why do you think those twitter meme abbreviations got wordfiltered? They don't belong here, and the mods know that.
