Seemed like a heavily improvised promo from Lesnar. There is like 1 percent probability that Brock was aware of anything that happened with R-Truth earlier this year, let alone knowing his real name, even though they might have worked together 25 years ago in OVW. And the segment with Brock, Killings and Heyman happened in January 2020, which was almost 6 years ago.
None of the stuff that Truth said meant shit to him, he has no idea about any other WWE storyline that doesn't involve him, and, since he is such a bad mic worker (he can be entertaining though as he was in late 2003, early 2004, and late 2021-early 2023), he simply got confused and forgot all the lines. And he knows he can get away with it.
All in all, even though I think that the last night segment was bad, I am very happy that Brock is back. As he said in 2012, he brings legitimacy with him.