I don’t think it was a retcon, so much as an alternate universe. Let’s be honest, the continuity of comics, is a fuckin mess.

But yeah, there’s a comic where Deadpool is the first human host for Venom and it causes Venom to go crazy, because he can’t deal with Deadpool’s multiple personalities and overall craziness.

Then he meets Brock, but Brock doesn’t bond at first, so venom finds Peter but because he’s weakened from Deadpool, Peter was able to fight Venom off.