Alright I did a bit of autistic detective work, so I'll share my thoughts.
Some people are saying that it could have been someone impersonating Pyro. I think it's unlikely. The oldest message Ivory has shown from his chatlogs was from March of 2017, and those still had heavy use of fatfurs. Pyro didn't start doing fatfur shit publicly til June 2017, as shown in the 4chan thread linked in the OP.
Also in the threads defending Pyro, there are videos of people talking about Ivory being a massive dicksucker. Since Ivory was indeed simping for Pyro, I find it very unlikely that he would fall for an imposter account. Ivory definitely had connections to Pyro and his crew, I mean his song appeared in a Lord Bung video for fuck's sake.
Also Ivory openly admits in his DM's with Pyro's gf that during 2017 and such, he was very open about sexual shit, both with Pyro and with many other people. He also described himself as acting very jailbaity. People have also said that he lied about his age, which is definitely possible considering how he was able to get away with this for so long.
Overrall, I definitely think he was doing this shit with Pyro, that account is definitely the real deal. However, there is one massive problem: Ivory claims he put his age on his Twitter bio, which Pyro must have seen since he followed Ivory. The thing is, I can't find any solid proof of his age in his bio in 2017. I've tried using the wayback machine, but it's not working atm.